The presidential race’s outcome may seem all but certain, but the race for Los Pinos has nonetheless received much more coverage than the legislative elections that take place on July 1 as well — and are just as vital to the comeback hopes for the Partido Revolucionario Institucional (PRI).

In addition to electing a president, Mexicans will elect 500 members to the lower chamber, the Cámara de Diputados, and 128 members to the upper chamber, the Senado.

If polls are accurate, not only will the PRI’s presidential candidate, Enrique Peña Nieto, win, but it will also win an absolute majority in the Cámara de Diputados — the first time that a party has won an absolute majority since electoral reforms in 1996, which would give Peña Nieto the best environment in over 15 years to pass legislation in Mexico.  A Mitofsky poll released yesterday shows that the PRI and its allies would win 44% of the Congressional vote to 29% for the PRD and its allies and 24.5% for the PAN.

Although the conservative Partido Acción Nacional (PAN) has controlled the presidency since 2000, first under Vicente Fox and then under Mexico’s incumbent president, Felipe Calderón, it never controlled an absolute majority of seats in the Cámara de Diputados and only from 2000-03 and from 2006-09 did it even hold the largest share of seats.  Given that dynamic, the PRI and the leftist Partido de la Revolución Democrática (PRD) have been able to unite in opposition to the PAN, frustrating the extent of Fox and Calderón to enact major reforms (although Calderón has passed minor tax reforms in 2005 and energy reforms in 2008).

Under the current rules, 300 deputies are elected on the basis of first-past-the-post plurality in single-member districts.  An additional 200 deputies are elected by proportional representation — each party that wins 2% is entitled to its share of seats.

No party, however, can win more than 300 seats in total — 200 seats must always be apportioned to opposition parties.  As most reforms in Mexico are “constitutional reforms” requiring a 2/3 supermajority, most major initiatives therefore require a broad base of support.  While that is of some assurance to those who are worried about the PRI’s authoritarian roots — Peña Nieto and the PRI won’t likely be able to push through legislation that would repress the gains of Mexican democracy — it also is the primary reason that Fox and Calderón have not accomplished any truly landmark legislative victories in the past 12 years. 

Furthermore, no party’s share of the total number of seats in the Cámara de Diputados can exceed its national vote by more than 8%.  So a party has to win at least a minimum of 42% of the national vote to have a chance at winning an absolute majority.  Even then, of course, 42% of the national vote may not be sufficient if the runner-up wins a sufficiently close share of the national vote as well or wins a larger amount of single-member districts.

So given that the PRI is right above the 42% mark in the Mitofsky poll, it seems on the cusp of winning that absolute majority — Mitofsky predicts the PRI will win between 270 and 300 seats to between 96 and 123 for the PRD and between 80 and 102 for the PAN.

The poll also predicts that Peña Nieto would win 45% of the presidential vote to just 29% for the PRD’s candidate, Andrés Manuel López Obrador, and just 24% for Josefina Vázquez Mota, the PAN’s candidate.  The presidential poll results are hardly surprising, and well in line with just about every other poll recently released, but the correlation between the presidential vote and the congressional vote is fairly striking.

While Fox won the presidency in 2000 by 7%, the PAN won just 1.3% more than the PRI that year in the lower house races and took 224 seats to the PRI’s 208 (and the PRD’s 65).

Indeed, by 2003’s midterm elections, even though the PAN won almost 8% more than the PRI, it ended up with just 151 seats to the PRI’s 224 seats (the PRD won 97).

When Calderón very narrowly defeated López Obrador in the 2006 election, with the PRI’s candidate a distant third, the congressional vote was much wider in favor of the PAN, which won 33% and 206 seats.  The PRD and its allies underperformed, winning 29% and 157 seats, while the PRI overperformed in the congressional race, winning 28% and 123 seats.

In the previous midterm elections in 2009, with Calderón reeling from an increasingly deadly engagement with Mexico’s drug cartels and the Mexican economy reeling from the worldwide economic financial crisis, the PRI won 36.5% and 241 seats (its ally, PVEM, Mexico’s Green Party — really an oddball PRI-affiliated party vehicle of the González family — won nearly 7% and 17 seats) to 28% and just 147 seats for the PAN and 12% and 72 seats for the PRD.

What makes this year’s congressional election so fascinating, however, is that the PRI could win enough votes to win an absolute majority on its own, without help from the PVEM.  Regardless, however, Peña Nieto will have an incredibly favorable legislative majority through at least 2015 — the likelihood that the PRI will pass reforms that it previously blocked under the Fox and Calderón administrations, including further moves toward Pemex privatization, is one reason, I suspect, Peña Nieto has built such a wide coalition of support, especially among business and other elites.