A powerhouse storm is forecast to soak a large part of the Midwest and South next Tuesday, Election Day.

This could influence the outcome of the elections: A recent study found that Republican candidates tend to have a slight advantage when it rains.

Tuesday's Election Day storm could feature wind-driven rain in the Great Lakes as well as rain and strong thunderstorms from the Ohio Valley to parts of the South, the Weather Channel said. Some wet snow – or rain changing to snow – is possible in parts of the upper Midwest.

Storms are forecast in some of the key battleground states for senators and governors, including West Virginia, Ohio, Indiana, Michigan, Tennessee, Mississippi and Georgia.

In contrast to the East, weather in the West should be best, AccuWeather said. Other than some pesky showers in Washington and Oregon, the weather is expected to be mostly dry for folks heading out to vote Tuesday.

Most of Florida and the Southeast coast will be quite warm and dry Tuesday.

One other trouble spot: Parts of the northern Rockies and high Plains could see some light snow that could make for slick roads on the way to the polls, the Weather Channel warned.

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So why does rain favor Republicans? Findings from the study revealed that at least 1 percent of voting age adults in the U.S. – people who would have voted for a Democrat had the weather been good – decided instead to cast their ballot for a Republican on rainy election days.

“Our study suggests that weather conditions may affect people’s decisions on not only whether to vote, but also who they vote for,” said study co-author Yusaku Horiuchi, a professor of government at Dartmouth College. The study appeared in the journal American Politics Research.

"Contrary to the widely shared belief that weather conditions do not change voters’ electoral decisions," the study said, "our analysis suggests that it is likely that a certain proportion of American voters would change their party preference depending on weather."

So apparently on Election Day, rain heightens pessimism and increases fears of risk: "Those who feel in an upbeat mood may lean toward the riskier candidate, while those who feel depressed and anxious lean toward the safer candidate," the study said.

Thus, "the choice for risk-averse people is to vote Republican," Horiuchi said.

Another expert, Mike Bender of the University of North Florida, told AccuWeather that voters affected by weather are borderline voters, folks who vote only occasionally. Demographically or socioeconomically, these borderline voters tend to be more liberal.