TOKYO, Oct 31 (Reuters) - The Mexico peso held firm in Asia on Monday, keeping some distance from a three-week low hit late last week following news that the FBI is planning to review more emails related to Democratic presidential candidate Hillary Clinton's private email server.
Market players cautioned, however, that the ramifications of the FBI's move are far from clear and that the peso, seen as the best barometer of the market's perception on the U.S. election, could slip further depending on upcoming polls.
The peso traded at around 18.96 to the dollar MXN=D2 , off its three-week low of 19.1005 touched on Friday, when it had fallen 0.7 percent.
Trading volume in the peso in Asia is much larger than the usual, according to Thomson Reuters data available at Eikon FX Volume Heatmap.
The peso is being used as a proxy on bets on the U.S. election because Mexico is considered to be the most vulnerable to Republican Donald Trump's protectionist policy as the country sends 80 percent of its exports to the United States.
"The support for Clinton seems to be falling sharply. Her victory does not seem secure as it was before. Having said that, the e-mail issue has been around and I'm not sure how much impact it will have," a senior emerging currency trader at a Japanese bank.
Clinton had opened a recent lead over Trump in national polls, but it had been narrowing even before the email controversy resurfaced.
In an ABC News/Washington Post poll, Clinton's lead over Trump shrank to 1 percent by Sunday from 12 percent just about a week ago.
Traders were also rushing to buy peso put options, or rights to sell the peso, to protect them against a victory by Trump.
The implied volatility on the dollar/peso options rose sharply, with one-month MXN1MO= volatility rising to above 20 percent, its highest level in more than two weeks, from near 15 percent just a week ago.
The FBI said on Friday it is investigating more emails as part of a probe into Clinton's private email system.
Clinton fought back, challenging FBI Director James Comey to provide a fuller explanation of investigative steps he is taking.