Admittedly there are a few to choose from - Mexico has an unusally wide array of highly opportunistic minor parties - yet in terms of two lacking near any semblance of a programmatic identity and real purpose beyond serving as franchises, as tools for their leaders, few beat the Partido Nueva Alianza (PANAL) of teacher union boss Elba Esther Gordillo, and, unchallenged at the top, the Partido Verde Ecologista de México (PVEM), the only rightwing Green Party in the world, which is not green, and not a real party.
Regardless: PRI's Political Commission just announced it will go in coalition with these two miscreants for the 2012 election in at least 126 districts, and for 10 senatorships. The PVEM's "Niño Verde," Jorge Emilio González Martínez, son of party founder Jorge González Torres, wants to be senator, and will likely get the candidacy.
Joaquín López-Dóriga has a very interesting column on the price PANAL wanted to extract from PRI - 30 federal deputies and 5 senators, reportedly. That is a very high price to pay for Gordillo's support.