Spot gold was up 0.8 percent at $1,278.38 an ounce by 2:54 p.m. ET (1854 GMT), after rising 1.3 percent to $1,284.14, the highest since Oct. 4. It is on track to close the week up 0.9 percent. U.S. gold futures settled up 0.6 percent at $1,276.80.
"The FBI headlines startled a somnolent gold market, driving bullion a percent higher in a hour on concerns that a late October surprise could suddenly bolster (Donald) Trump's sagging fortunes," said Tai Wong, director of base and precious metals trading for BMO Capital Markets in New York.
"The rally may not last, though, as we are at the two-minute warning and Clinton is ahead by two scores, so it would require a truly shocking revelation to derail her chances." Wall Street and the dollar fell against a basket of six major currencies after the Federal Bureau of Investigation said it would probe additional emails related to Clinton while she was secretary of state.
The greenback was already weak, having shrugged off slightly better-than-expected U.S. third-quarter GDP data amid firm demand from Asia.
The U.S. economy grew by 2.9 percent in the third quarter, outpacing analysts' consensus forecast of 2.5 percent. The data strengthened the case for an interest rate increase, making non-yielding assets such as gold less attractive while boosting the dollar and U.S. treasuries.