I have to say that these are the oddest bunch of parties! Greens who support the death penalty! Left and far right......we may be able to see some similarities but they usually can’t.
Yes, it's the oddest bunch of parties.
It's never been "normal" in the European (or Australian) sense, since the PRI has always been a sort of Macheavellian catch-it-all party. Until the late 80s PRI had all the Federal and State Executive branches, so many people who wanted to make a professional career started as PRI militants.
PRI is still a member of the Socialist International, though it was an authoritarian party for many years, and has moved consistently to the right in economic matters, at least since 1982.
The Green Party was founded in the early 90s and true greens were sidelined as it became a political business for the founder and his family. The son of the founder - nicknamed "The Green Boy" when he got to preside the party, but now over 50- swiftly converted it in a sort of rich boys club, and moved it to the right. It has been allied to PRI since 2006.
Panal, the teachers' union party, went alone in 2012, and it didn't go well for them. Since then, they have sided with PRI to have their secure berths.
The other strange phenomenon is Andrés Manuel López Obrador (AMLO), a politician made in the PRI, who moved to PRD when he was not handpicked to be governor of his native state, Tabasco (South).
AMLO went on to take hold of PRD (another member of the Socialist International) and was their presidential candidate in 2006 and 2012. In 2016 he lost for less than 1%.
His authoritarian and populist vein made it difficult for him to keep the reins in the PRD, so he broke with them and founded his own party (Morena).
Morena took almost half of PRD former voters in the midterm 2015 elections and is growing.
AMLO is a charismatic politician, and many of his followers adore him. He has been called "the tropical Mesiah" by one of his critics. Morena has moved from the left to an strictly more Nationalist approach.
AMLO himself is a political extremist but a social conservative. This explains his ability to gather around him both the Maoists and the Evangelical Christians. What baffles me is that some liberal leftist still believe in him.
Someone said: "He has not a party, but a community of the faithful".
The fact that the remaining left wing party (PRD) lost half its power to AMLO and Morena put them in a difficult position. If they competed alone, they may lose their strongholds, most notably Mexico City, and become irrelevant. And the PAN conservatives wanted to beat both PRI and AMLO, so they thought of a wide alliance.
PAN and PRD have one thing in common: they have been committed to democracy.
MC (Citizen's Movement) is strong in some states, notably Jalisco, and its capital, the second most important city, Guadalajara. Their bet is to win the State, which also has great PAN following.
So, in terms of logic, the three parties divided the cake: Presidency for PAN, Mexico City for PRD and Jalisco for MC.
Alas, an explanation (sort of)