An important basis for the support they receive in elections is the strong patron-client network the PRI still maintains.
The national candidates are trying to convince voters to support their agenda, just like the other political parties.
This is a departure from the past, when the PRI could be characterized as a dominant party with no definitive ideology other than to get reelected and stay in power.
The pendulum of the mid-twentieth-century presidents vacillating between state-driven and market-driven economic policy is evidence of the PRI's ideological flexibility.
The ideology of the modern PRI is usually characterized as centrist, center-right, embracing recent capitalist and globalizing reforms, while advocating for welfare policies to address the needs of lower class Mexicans.
Working-class or rural Mestizos were the most likely to vote for the PRI in the last three presidential elections.
After the election of Vicente Fox in 2000, the PAN became the PRI's opposition to the right, and Felipe Calderon became the president.
From 2000 to 2009, the PAN held a plurality of seats in the legislature, but never held a majority.
Free enterprise, privatization of national industries, trade liberalization, and small government are some of the policies supported by the PAN.
Fox's inability to navigate governing Mexico without the PRI's network was one of the reasons he had difficulties implementing most of the PAN agenda.
The PAN is a socially conservative party in Mexico that enjoys the support of the Catholic Church because of its stances against abortion and same-sex marriage.
Those who live in the northern region, those who work in the private sector, and those who make better than average incomes are the most likely to vote for the PAN in Mexico.
The PRD has been the opposition to the left since it broke away from the PRI after the fraudulent 1988 election.
It has supported an ideology centered on human rights and social justice for disadvantaged groups in Mexico, drawing particular support from the southern region with the highest concentration of poor and indigenous Mexicans.
Mexico's labor unions are declining in power because of globalization and free trade, but the PRD performs well in urban areas.
Obrador called upon PRD supporters to gather in Mexico City to protest the results after he almost won the presidency.
He was the runner-up in 2012 for the second year in a row.
The PRD barely crossed 10 percent of the vote in the PR portion of legislative elections in 2015, after getting over 20 percent in recent elections, as Obrador left the party to form another called the National Regeneration Movement.
After losing the 2012 elections, Lopez Obrador created MORENA.
Mo vimiento Re generacion Na cional is also known as the National Regeneration Movement.
In the first election of its kind in Mexico, the coalition of left- and right-wing groups won 47 out of 500 seats in the Chamber of Deputies.
MORENA claimed the most seats of any party in Mexico's Senate and Chamber of Deputies in the first elections it competed in.
Mexico is a federal state with many different levels and different branches of government.
Legislators will be able to be reelected to a limited number of terms now that reforms have been signed into law.
Governors and presidents can only serve one sexenio.
Mexico's president is directly elected every six years.
Party machinery would fall in line to arrange the orderly election of the incumbent president's successor under the rule of the PRI.
The elections are generally believed to be free and fair.
Voters cast their vote after each party nominates a candidate for the presidency.
Regardless of whether the candidate received a majority or plurality, the candidate with the most votes wins the presidency.
In the last two elections, the system has come under scrutiny as presidents were able to win with less than 40 percent of the vote.
The system never produced results like this before, as the candidates for president of the PRI would usually receive over 90 percent of the vote.
Many recent presidents have faced questions about the legitimacy of their election because of the modern three-party competitive structure, which makes it difficult for a candidate to govern with a majority "mandate" from the people.
After the 2006 election, election observers from the EU made a recommendation to change to a two-ballot majority system, with a run-off between the top two candidates if no one gets a majority in the first round.
Presidents can't run for a second term under the principle of non-reelection.
In previous elections, candidates needed to be affiliated with a nationally registered political party in order to run, but starting with the upcoming presidential election, independent candidates will be able to run as well.
The candidate with the most votes wins the presidency regardless of whether or not the candidate has a majority.
The Chamber of Deputies and the Senate are the houses of the Congress of the Union in Mexico.
There are 500 members in the Chamber of Deputies, each elected to a three-year term, 300 of whom are elected from single-member-district (SMD) constituencies based on which candidate gets a plurality (not necessarily a majority), and 200 of whom are elected by proportional representation.
Legislators can run for up to four terms now that they are allowed to serve one single three-year term.
The Senate of the Republic has 128 senators.
The first 96 seats are filled by three senators from each of Mexico's 31 states.
The parties can run two candidates in the same state.
The party that gets the most votes in the state will have both of their candidates elected.
The third seat for each state goes to the party with the second most votes.
According to an IFE rule from 2000, women must make up at least 30 percent of the party list.
Thirty-two seats in the Senate are awarded in a PR system based on the party's performance in a nationwide vote.
After their first term, senators may run for an additional term.
Mexico's legislature has been characterized by gridlock since the reforms of the 1990s, despite the fact that it was relatively easy for the PRI to manage elections to ensure a large legislative majority.
Since the 2000 election, no single party has held a majority of both houses, and the PRI has been able to form governing coalitions with smaller parties.
MoreNA's coalition has majority control of the Chamber of Deputies, but no coalition has a majority in the Senate.
Each of Mexico's 31 states directly chooses a governor to a six-year term, though the years of the election are staggered state-by-state.
Local officials such as mayors are also elected by voters.
These races have become more competitive in Mexico's democratic transition, since they were once completely controlled by the PRI.
The rise of an independent interest group system was caused by reforms in the 1980s and 1990s that broke the model of the PRI's arrangement of state corporatism.
The Confederation of Mexican Workers is a pillar of the PRI.
The collapse of oil prices and the start of austerity imposed by the International Monetary Fund reduced the power of the union, especially as the PRI administrations negotiated and signed free-trade agreements.
As unions lost power within the PRI to the new technico elites, the Ctm took a conservative stance opposing any change to the status quo of PRI domination and was perceived by workers to negotiate disputes in favor of the employer more and more often.
Workers turned to independent unions as the legitimate voices for their concerns, and the Ctm is now just one of many voices drawing attention to labor concerns.
The media was manipulated by the PRI during its time in power.
The variety of media outlets were privately owned.
The PRI would pay journalists directly to write stories for friendly media outlets.
PRI candidates for office and state-owned companies controlled by PRI-connected executives would only advertise in cooperative media; official announcements, state industry ads, and PRI campaign ads could account for as much as two-thirds of revenue for many media companies.
It was nearly impossible for an outlet to stay open if they didn't cooperate with the PRI.
In the 1980s structural adjustment austerity limited the state's ability to pay for expenses like media coverage and most of the state subsidies to media were eliminated.
There are many ways for Mexican news consumers to get their news.
Vicente Fox's many public gaffes were covered by the media during his time in office, as it demonstrated independence in its willingness to criticize the administration.
Many Mexicans were concerned about the media bias in favor of the PRI since Televisa, Mexico's largest media conglomerate, used much of its programming and print to cover the governor of the state of Mexico.
The Constitution of 1917 created Mexico's state institutions.
Mexico's political culture and functional political processes have changed a lot, but the structural institutions have not.
The president of Mexico is elected to a single six-year term and acts as both the ceremonial head of state and the head of government.
Most of the presidents of Mexico have had their own armed power base.
Presidents are not allowed to have served in the military for more than six months before the election.
The constitution gave the president broad powers, as well as huge influence over party affairs.
The Mexican executive was often characterized as a six-year dictatorship, as presidents would fill every level of government with political loyalists, creating a massive patron-client network with the president at the top.
Most of the power at the federal level of government is given to the president.
The president's powers are limited by the Constitution.
In the twentieth century, the president was not as important to the Mexican political system as he is today.
Mexican citizens still think the president is responsible for all political outcomes, positive and negative.
Both houses of the Mexican Congress of the Union exercise meaningful power in policymaking.
After opposition party deputies were elected out of 500 seats in the 1988 election, it became a check on the president's power.
Even though the PAN held a plurality through 2009, it was difficult for President Fox and President Calderon to pass reforms because of the new norm of gridlock in the legislature.
After 2012 the PRI party had difficulties in leading seats.
The Supreme Court of Justice in Mexico is made up of eleven judges who are appointed to fifteen-year terms by the president.
Judges can be nominated for more terms.
The Supreme Court of Justice appoints the judges at lower-level courts.
The system of judicial appointment used to be part of the PRI's patron-client network, however, reforms in 1995 created a merit system for prospective judges to prove their qualifications before they can be nominated.
The reforms are making the judiciary more independent.
The Supreme Court of Justice has the power of judicial review to strike down laws that are unconstitutional, but only if at least one-third of the Congress, one-third of a state congress, and the attorney general ask them to do so.
Code law is the basis of Mexico's legal system.
Detailed legal codes enacted into law by Congress or presidential decree answer most legal questions.
In a common-law system, judicial precedent does not play a role in the interpretation of laws.
Many Mexicans don't trust the courts because of the long history of patron-clientelism and corruption.
There are still frequent complaints against judges even though Felipe Calderon tried to crack down on corruption.
Most of them are small and related to a lack of competence among state level judges.
There are still troubling cases in which judges have been bought off by drug traffickers or threatened with violence in exchange for favorable rulings.
The 2008 reform that required trials to be public by 2016 was the reason why trials were not held publicly.
Over 1.5 million people work in Mexico's bureaucracy.
The bureaucracy was thought to be corrupt and incompetent when it was part of the patron-client network.
Most bureaucrats were not familiar with their jobs when the head of an agency was moved to a new agency as a new president took office.
Mexicans would expect bribes from bureaucrats in order to get approvals or certifications.
During the one-party rule, the bureaucracy was part of the president's patron-client network, but during the democratic transition, it has become more professional and non-partisan.
The bureaucracy is notorious for being corrupt.
One of the first orders of business for the PAN was to professionalize the bureaucracy.
The result was a massive codification of regulations called tramites, which established procedures meant to prevent incompetence in the bureaucracy.
Mexicans became incredibly frustrated with the large number of tramites, making repeated trips to government agencies, and waiting in long lines for even the most basic approvals for things like trash collection.
The Mexican said he paid $250 in bribes to get approval to paint his house.
A $50,000 cash prize was offered to anyone who could identify the most unnecessary tramite, and over 20,000 nominations were received.
Over 4,200 tramites are on the books, and Mexicans have paid more than $2 billion in bribes to bureaucrats in the last year.
The military dominated Mexican politics in the 19th and 20th century.
From independence through 1946, nearly every head of state was a general.
Military officers had to be out of the military for at least six months before taking any other official position.
The president is the supreme commander of the military.
Ensuring the subordination of the military was a priority for the early PRI presidents to prevent the instability and constant threat of coups that had plagued Mexico prior to the formation of the PRI.
Presidents Cardenas and Calles, both former generals themselves, have a policy of rotating the command posts of their generals to prevent them from building an independent base of political power in any region.
Some of the state-owned companies provided lucrative positions for generals to prevent them from getting into politics.
Today's military is largely professional and depoliticized, firmly under the control of the elected officials, with no sign that they will intervene in Mexico's political system anytime soon.
Mexico was constitutionally federal, but state governments were essentially puppets of the president.
The states have been given a new independence and significance because of election reforms.
Each of Mexico's 31 states has its own governor and congress.
Governors can only serve a single six-year term, and legislators can only serve one term at a time, though they may run for election for additional nonconsecutive terms.
Mexico is both constitutionally and functionally federal.
States have a wide range of powers within their borders.
Mexico was once classified as a less-developed or developing country with an authoritarian political system.
Voters and political elites must navigate new policy concerns in order to ensure the survival of the reformed regime in Mexico.
Since the fiscal crisis of 1982, Mexico's economic policies have moved in a completely different direction.
Mexico has embraced globalization and free trade as part of its development strategy.
The North American Free Trade Agreement was very successful in bringing new higher-wage jobs to the northern region, and also to maquiladora districts where factories can import raw materials duty and tariff free, and export to any market around the world with no restrictions from the Mexican state.
The early successes slowed as the United States traded with China and other low-cost manufacturers; whereas maquiladora factories were once responsible for 17 percent of employment in Mexico.
In many cases, Mexican factories are the best option for employment because they pay very low wages.
There is still debate about the effectiveness of the North American Free Trade Agreement in Mexico.
Since the introduction of the North American Free Trade Agreement, Mexico's economy has grown at a rate of 1.5 percent per year, but the gap between rich and poor has grown.
Estimates show that the costs of basic household goods have been cut in half, allowing many Mexicans to live better than before.
Poverty has gone up.
Subsidized U.S. agricultural products flooded the Mexican market and put many farmers out of business, possibly contributing to the wave of illegal immigration into the United States.
Since the signing of the North American Free Trade Agreement, agricultural exports from Mexico into the United States have tripled, suggesting it may be creating more farm jobs than it has cost.
There will likely be political conflict over the next many years.
A program called opportunidades is part of Mexico's strategy to deal with rising poverty.
The government makes cash payments to mothers in poverty if their children attend school regularly and follow certain nutrition guidelines.
The program has been very successful in other countries.
After the influx of oil revenue in the 1970s, large state-owned, yet independent business operations were created in Mexico.
Parastatals were protected from foreign competition through 1982.
The fiscal crisis required Mexico to eliminate many of its trade barriers as part of structural adjustment, and parastatals began losing huge sums of money against their far more efficient competitors.
In the 1980s and 1990s, the government sold most of these firms.
The largest and most significant, the national oil company, Pemex, was tried to privatize by President Fox.
Fox was unable to get this agenda passed through Congress, and Pemex has remained a source of frustration for its inefficient production and operating losses that the state must subsidize.
Foreign oil exploration companies are now allowed to drill in Mexico on a limited basis, as the president has reformed the oil market by allowing limited foreign competition.
One-third of Mexico's annual budget is funded by taxes paid by Pemex.
The tax structure in Mexico is being changed to make it possible for Pemex to survive against foreign companies, while at the same time making the government less dependent on Pemex revenue.
In response to a wave of violence that overtook many cities in the north, Mexico has been engaged in a war on drugs.
Drug traffickers are competing for control of distribution networks into the United States.
Local officials, including the police, were bribed to ignore the activity of the cartel.
As Presidents Fox and Calderon tried to root out local corruption, they saw opportunities to move into territory previously held by other rival gangs.
Local officials and reporters who try to stop the activity of the drug traffickers are often murdered.
Between 60,000 and 120,000 people have died from drug-related violence so far.
President Fox used the Mexican military to carry out high-profile campaigns against the drug gangs, and though he criticized the strategy for bringing about too much bloodshed, he followed a similar strategy with much more success.
The situation in Mexico appears to be stabilizing and many of the high-profile leaders of the drug gangs have been brought into custody.
Mexico has had a major problem with corruption for many decades.
Mexico was ranked 135 out of 180 countries on the Corruption Perceptions Index.
In the small town of Iguala, 43 students were kidnapped and burned to death in the summer of 2014).
The mayor and his wife ordered the kidnapping because the students were going to disrupt an event where the wife would announce her plans to run for mayor.
The president has had to contend with corruption concerns.
The First Lady's mansion was built by a contractor who received part of a $4.3 billion rail contract from the government.
It was questionable for someone who worked in civil service for their entire career to be worth more than three million dollars in the middle of his presidency.
Congress passed an anti-corruption law in 2015.
The reversal of longstanding impunity in Mexico remains to be seen.
Mexico's foreign policy has always been focused on the relationship with the United States.
There are many reasons why the United States is so important.
The majority of Mexico's exports are to the United States.
Remittances, payments sent back into Mexico from workers in the United States, make up 2.1 percent of Mexico's GDP.
Mexico is the third largest trading partner of the United States.
After the terrorist attacks on September 11, the priorities for the United States changed from economic integration to counterterrorism and security.
The United States in the North American Free Trade Agreement was criticized by President Donald Trump.
The negotiations with Canada and Mexico followed his threats to pull the United States out of the agreement.
Minor modifications to tariffs and quota in a few industries of concern, including automobile manufacturing and dairy products, were the result of these negotiations.
The United States-Mexico-Canada Agreement is now referred to as the United States-Mexico-Canada Agreement, or USMCA, as opposed to the North American Free Trade Agreement, though its final approval is still pending.
Immigration is a difficult issue between the two countries.
Mexican presidents have supported loosened U.S. immigration restrictions to allow Mexican guest workers.
The United States never created a guest worker program and built a massive border fence to stop illegal immigration from Mexico.
The Berlin Wall was compared to the fence by the President.
Many U.S. policy responses push the boundaries of Mexico's sovereignty, with American police, military, drug enforcement agents, and drones patrolling Mexico in search of drug-related criminals.
Mexico has signed free-trade agreements with 44 different countries.
Mexico joined the World Trade Organization in 1995 and is now a member of the United Nations.