Mexico has its elections for President, Chamber of Deputies, and Senate on 1 July. It has been clear for a while that, barring a big surprise, Andrés Manuel López Obrador (popularly known as AMLO) will win.
AMLO’s support has risen steadily out of what looked like a tight three-way contest some months ago into a strong lead. When voters responding “no preference” are removed, it even looks likely that AMLO could win a clear majority of votes. Mexico elects its presidency via nationwide plurality, and no Mexican president has earned half the votes since 1994 (at a time when most experts still considered the regime authoritarian, albeit increasingly competitive).
Assuming AMLO wins, it will highlight the competitive three-party nature of the system. When the center-right National Action Party (PAN) won the presidency in 2000, it broke decades of continuous control by the Institutional Revolutionary Party (PRI). The PAN won again in 2006, on less than 37% of the votes in a very tight race, with AMLO close behind (and refusing to acknowledge defeat). The PRI returned to the presidency in 2012, and now AMLO will give the left its chance. (AMLO was with the Party of the Democratic Revolution, PRD, but in recent years has set up a new party, MORENA, while the remnant PRD is backing the PAN candidate this time.)
I would be very interested in seeing an analysis of AMLO’s own manifesto (and his party’s, if separate). There is much hand-wringing over his leftist “populism”. However, when he ran in 2006, he staked out a centrist economic platform well to the right of his own party–a clear case of what “presidentialization” does to parties. (See the discussion of the general point, and also the 2006 Mexican campaign, in my book with David Samuels, Presidents, Parties, and Prime Ministers). Is he doing so this time? I can’t claim to have followed closely enough to know.
As for the Chamber of Deputies, if the pattern of recent Mexican elections holds, the party winning the presidency will win fewer votes for its congressional candidates. That could mean MORENA (and pre-election allies) will not have a majority of seats. On the other hand, as noted above, these previous presidents have not themselves won majorities. Moreover, the electoral system is mixed-member (with the voter having a single vote). It is sometimes erroneously categorized as mixed-member proportional (MMP), but it is actually leans much more to the majoritarian category (MMM). Seats won based on nationwide votes for party are added to single-seat districts won (by plurality).
The allocation is not compensatory, but it is also not strictly parallel. There are caps on allowable over-representation (unlike in a “pure” MMM system). The most important cap is that no party can have a final seat percentage that is more than eight percentage points above its vote percentage. Thus if a party wins under 42% of the votes, it is unable to have a majority of seats. If it gets over 42% it is not guaranteed a majority, but a majority becomes likely, due to the non-compensatory nature of the allocation. This cap kept the PRI from retaining its majority in the midterm election of 1997, and I believe it has been hit in several subsequent elections, as well. This is what I will be watching most closely: Will MORENA (and allies) get a Deputies majority?
The Senate is also elected in a mix of regional and nationwide seats. Each state has three senators, elected by closed list, limited-nominations plurality. The largest list gets two seats and the runner up gets one. Then there are 32 seats elected by nationwide proportional representation (allocated in parallel, not compensatory manner).
These provisions, combined with the regionalization of party support in Mexico, make it difficult for a party (or alliance) to win a majority of the Senate’s 128 seats. AMLO is unlikely to have majorities in both houses, but it is worth noting that the federal budget must clear only the Chamber. There is no Senate veto on the spending side of the budget, although both houses must pass all other types of bills. Thus the left will be in a strong, but not unchecked, position to implement its program for the first time in Mexican democratic history.