The peso gained more than 2 percent against the dollar, leading major currencies. A final battery of polls this week showed Andres Manuel Lopez Obrador held a wide lead ahead of Sunday's vote.

The peso has clawed back from a 1-1/2 year low it hit in the middle of the month. Traders and analysts said the peso had priced in a victory by Lopez Obrador, who again insisted at a closing rally Wednesday he would not raise government debt.

However, the peso could weaken if Lopez Obrador's party gains majorities in both houses of Congress, which could allow for more significant changes to economic policy, a traders and analysts said.

Also supporting the peso, Mexico's central bank deputy governor Javier Guzman suggested at a conference in London that policymakers could hike interest rates again, if needed, according to a presentation published Thursday.

"(Guzman) considers that there's a palpable risk in inflationary pressures, which elevates the probability of another interest rate increase and at the same time reduces speculation against the peso," Banco Base said in a report.

Brazil's real gained about 0.5 percent after a rout on Wednesday, while a key poll showed Brazil's left failing to gain steam in presidential elections scheduled for October.

On Wednesday, the real led losses across the region, falling over 2 percent. A decision by a Supreme Court Justice that all privatizations in Brazil must be approved by Congress also hit the currency.

The poll conducted by industry group Ibope showed far-right congressman Jair Bolsonaro leading with 17 percent support, followed by environmentalist Marina Silva. Center-left populist Ciro Gomes registered 8 percent support.

Across the region, equities markets were mixed with Brazil's benchmark Bovespa index the big winner, climbing 1.6 percent.

Separately, Mexican breadmaker Bimbo said on Thursday it had completed the acquisition of Chinese breadmaker Mankattan, a deal originally announced in February.