(Bloomberg) -- The "Trump ETF" is predicting an unpleasant evening for the Republican presidential nominee.

The largest, U.S.-listed, Mexican ETF posted its highest gain in five years on Monday, closing 5.1% up after taking in almost $125 million. The largest daily inflow in three years came as markets reacted positively to Hillary Clinton's strengthening prospects for victory in the final days of the U.S. contest.

The New York-listed iShares MSCI Capped ETF — which gives investors exposure to Mexican stocks and, by extension, the peso — has been on a roller-coaster ride in recent months, tracking the ebbs and flows of Donald Trump's electoral fortunes. The ETF has added credibility to the consensus view that a Republican victory would deliver a significant blow to Mexico's economic prospects.

The strength of flows into the ETF — with daily trading volumes currently averaging $400 million — reflects the fact "it is probably the most sensitive ETF to poll numbers," Eric Balchunas, ETF analyst at Bloomberg Intelligence, said on Bloomberg TV. 

"It is not unusual to see a single-country ETF become the way to bet an on election," he added, but "here you have an ETF not of our country that has become the proxy to bet on the election."

Watch how the iShares Mexican ETF — in addition to the peso — trade on Tuesday and in the aftermath of the U.S. election for clues on how investors are reacting to what might be one of the most consequential U.S. political campaigns for emerging markets in modern times.

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