(Bloomberg) -- Mexico’s presidential frontrunner Claudia Sheinbaum saw her commanding lead in some opinion polls narrow less than a week before election day in Latin America’s second-biggest economy. 

Sheinbaum, the candidate of President Andres Manuel Lopez Obrador’s ruling Morena party, has consistently led by more than 20 percentage points in most polls throughout the campaign.

A pair of surveys released Wednesday, the last day the law permits the publication of polls, still have her with a double-digit lead but show an erosion of support that could cost Morena some seats in congress.

In an AtlasIntel poll released Wednesday, Sheinbaum’s lead decreased to 13.3 percentage points, garnering the support of 48.2% of those surveyed, compared to 34.9% for the main opposition candidate, Xochitl Galvez, and 16.1% for distant third-place candidate, Jorge Alvarez Maynez. 

The AtlasIntel poll results are similar to those of another poll published Wednesday that showed Sheinbaum leading by 12 points, down from 15 points in April. AtlasIntel successfully anticipated the results of Brazil and Argentina’s presidential elections in 2022 and 2023, respectively.

The percentage of people saying they will vote for Sheinbaum is at 51% in the most recent poll by the Grupo de Economistas y Asociados (GEA) and Investigaciones Sociales Aplicadas (ISA). Galvez has a 39% of support and Maynez 10%. 

In the GEA-ISA poll, approval for outgoing Lopez Obrador declined slightly to 49% from 50% previously. 

Poll Tracker

In the latest edition of Bloomberg’s Poll Tracker, Sheinbaum’s lead has also narrowed, although at a very slow pace: She has 55.3% of voter intention, a 21.3 percentage-point lead over Galvez, who has 34% of support. The Mexico Bloomberg Poll Tracker is based on a weighted system of polls based on a series of criteria including the quality of the methodology.

Besides the president, Mexicans will elect 628 seats in both houses of congress, the new Mexico City mayor, eight governors and multiple local positions. 

The bigger Sheinbaum’s victory, the greater the possibility that the government coalition parties could secure a simple majority or even a two-thirds so-called super majority in congress, which will allow the new president to pass the constitutional reforms that Lopez Obrador was unable to approve due to the opposition’s strength in congress. 

The AtlasIntel poll surveyed 4,084 people digitally between May 25-28 with a margin of error of +/- 2 percentage points. The GEA-ISA poll surveyed 1,070 people in person at their homes between May 23-26 with a margin of error of +/- 3 percentage points. 

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