The leftist party of presidential hopeful Andres Manuel Lopez Obrador was in a photo-finish race to strip control of Mexico's most populous state from the country’s ruling party, polls showed on Wednesday.
A victory in Sunday's election in the State of Mexico would hand Lopez Obrador's three-year-old party its first state government, showing its anti-corruption message has mass appeal and adding momentum to his run for the presidency in 2018.
Mexico's ruling Institutional Revolutionary Party (PRI) has governed the State of Mexico, which rings Mexico City, for nearly nine decades.
Financial markets are closely watching the progress of the strong-willed leader with nationalist leanings. If he does win in 2018, it could stoke tensions with the United States after President Donald Trump's populist broadsides against Mexico during his own election campaign.
A poll in national newspaper Reforma showed Delfina Gomez of his National Regeneration Movement (MORENA) party had 31.9 percent support to be governor of the state of 16 million people where one in eight of the nation's voters live.
The PRI candidate, Alfredo del Mazo, who is battling against a widely held view that his party is corrupt and has failed to rein in crime, was behind with 30.7 percent. However the gap between the two candidates was within the survey's 3.2 percent margin of error.
A second poll, in another national daily, El Universal, showed del Mazo ahead with 33.8 percent of support, while Gomez had 29.3 percent. In both surveys the two candidates had increased their support since earlier polls.
Wednesday is the last day of campaigning for the election.
Votes will also be held on Sunday in the states of Coahuila and Nayarit, both also governed by the PRI.
President Enrique Pena Nieto, also of the PRI, is a former governor of the State of Mexico. His party is struggling to overcome graft scandals and rising crime in states it governs.
It portrays Lopez Obrador in the mold of Venezuela's left-wing leaders. However, the veteran campaigner has moderated some economic policies in his third bid for the presidency and no longer vows to overturn an energy reform ushered in by Pena Nieto.
The Reforma poll was conducted through 1,200 interviews at home between May 24 and May 29. El Universal's poll held 1,000 face-to-face interviews between May 26 and May 29 and has a 3.1 percent margin of error.