Let me give you a more balanced, proper context:

The one-party state started fading in the 1980s. When Reagan and Thatcher entered the world stage, Mexican politics shifted from the pseudocommunist rule (PRI) to a liberal form. It was still presented as a state party (PRI) but started making concessions to competitors in local elections, and congress (opposition parties have existed since the 1930s, they were just unable to win because the entire thing was rigged).

During the 90s, the political landscape had three major parties: Conservatives (PAN), Liberals (PRI), and a Leftists (PRD), this last one was founded in 1988 when the more leftist part of PRI left their ranks denouncing this political shift I explained earlier. Picture AOC and her gang leaving the democrats because they were becoming too moderate.

In the 2000 presidential election, the conservatives (PAN) won. The most relevant context I can give you for this, is the assasination of PRI’s presidential candidate in the previous election (1994) and the economic crisis of December of that same year. Both events created a general sense of instability within the ranks, and the conservatives took the opportunity in the following elections.

When PAN took over, on the very first month of their government, one major event happened: Chapo Guzman escaped prison, and for the following 15 years he slowly terrorized the country and became the famous person he is now. Organized crime (cartels) thrived since the 1970s, but Guzman was from a new generation of criminals, much more willing to make super public and super violent statements.

After the first PAN administration, some things improved, a lot of institutions became much more legit or democratic because the very fact of changing parties enhanced the checks and balances. But crime was still on the rise and top government officials and criminals were still heavily intertwined (more on that later).

At the beginning of the second PAN administration (reelection is not legal in Mexico, so new guy), the President decided to focus most, if not all of his efforts on stopping crime in what was called “the war against narcos”. He signed a cooperation agreement with the US (Merida Initiative) and waged an all out war against them. The results were disastrous. Crime rose like never before and some key battlegrounds experienced violence on the same level of the war in Iraq. Michoacan, Tamaulipas, Juarez, Tijuana were almost fully controlled by Cartels, and Chapo Guzman’s Sinaloa Cartel grew exponentially.

The end result was conservatives (PAN) dropping to third place in the 2012 Presidential Election and people opting for giving another chance to PRI. Chapo Guzman was promptly captured, managed to escape again and recaptured (PRI managed to capture him twice in a single term, while PAN failed to do so in two full terms). But crime didn’t stop. The concept of politicians being killed was already normalized at this point. PRI’s return to power failed, but they managed to put the public eye away from cartels and crime. They started talking about passing legislation, modernizing the economy, and so on. They even legalized same-sex marriage, to give you an example.

In 2018, a newly formed left-wing party (MORENA) won by a landslide, leaving PRI, PAN and PRD trailing by dozens of points. The current President has focused in building a welfare state, creating social programs, strengthening unions, worker’s rights, increasing the role of the state in the economy, and a generally leftist platform. But in terms of crime and violence, things have been basically the same. Not more crime than before (if you take population increase into account), but also not diminishing it.

Notably, during this past couple of years, the United States aprehended Genaro Garcia Luna, a key intelligence official under PAN’s first term and Secretary of Security (the guy in charge of fighting cartels) during PAN’s second term. He was found guilty of being part of Chapo’s cartel and currently in prison. Chapo’s rise during both PAN’s administrations now has an explanation. This also sheds some light on this political violence — the line between politicians and criminal organizations is often blurred or non-existent (I’m not criminalizing the victims, sometimes the crooked guys are their rivals).

Mexico will have its Presidential election in 6 weeks. PRI, PAN and PRD are now running the same candidate to face MORENA. Polls suggest a similar MORENA landslide will happen, but polls are prone to fail. So, the party that managed to defeat the state party are now effectively trying to bring it back, but this time they merged with them.

Hope this helps.