According to one forecasting firm, Hurricane Sandy will "end up causing about $20 billion in property damages and $10 billion to $30 billion more in lost business," and as of Tuesday evening the superstorm had left millions without power in the Northeast and claimed the lives of 45 people on the US mainland.

Though Hurricane Sandy will be long over by the elections next week, its massive disruptions will still be a part of life for many voters in the eastern United States, and election day weather forecasts show subsequent weather patterns that, together with the Hurricane Sandy effect on election turnout, could deliver a blow to Democratic candidates, including President Obama, on Election Day.

In 2008, record high voter turnout (the highest since 1968) swept Obama to electoral victory and other Democratic candidates rode his coattails to massive gains in the US House and Senate. But with billions in property damage to the East Coast, including key swing states like Virginia, Pennsylvania, and Florida, turnout is likely to be dampened by Hurricane Sandy, which already ground early voting to a halt in some states and may have prevented some eligible citizens from registering to vote by their state's deadline.

Workers in hospitals, repair and maintenance businesses, construction companies, utilities companies, and infrastructure will be working overtime to recover from the storm damage. Voters whose lives have been disrupted by evacuations and heavy flood or storm damage to their property and places of residence will be busy putting their affairs back together and may find themselves unable or unwilling to vote on Election Day.

There will also be last minute changes to voting locations due to storm damage and flooding, and these changes will be managed by Republican administrations in all three of the swing states named above. State officials are likely to be short-staffed for the election as well, focusing on public safety issues, infrastructure repair, and other hurricane recovery efforts.

The weather on Election Day itself also has a profound effect on voter turnout. A 2007 study by the Journal of Politics found that rainfall decreases voter turnout by a factor of about one percent per inch. The study, titled "The Republicans Should Pray for Rain," reports in its abstract:

"Poor weather is also shown to benefit the Republican party's vote share. Indeed, the weather may have contributed to two Electoral College outcomes, the 1960 and 2000 presidential elections."

Election Day precipitation benefits Republican candidates because Democrats are statistically less likely than Republicans to turn out and vote on a rainy or snowy election day. A survey of voters reported by the Weather Channel on September 25th found that 27% of Democrats report that "bad weather conditions" could moderately to significantly impact their ability or willingness to make it to the ballot booth as opposed to 20% of Republicans.

As of Wednesday morning, AccuWeather's Election Day precipitation forecast reported a 50% - 75% probability of precipitation covering much of the key swing states of Pennsylvania, Virginia, and Florida --with a 75% - 100% probability of precipitation in the southern half of Florida. Cross-referenced with a map of 2008 presidential election results by county, the AccuWeather forecast reveals precipitation in all the worst places for Democratic turnout on Election Day:

In Pennsylvania, precipitation is expected for the eastern half of the state with most of the state's bluest counties in the densely-populated Philadelphia area. Rainy weather is forecast to cover most of Virginia on election day as well, including quite a few red counties, but will leave many of the commonwealth's northern red counties on the West Virginia border untouched, while affecting nearly all of northern Virginia's blue counties, including its densely-populated counties on the border of Maryland and the District of Columbia.

In Florida, rainfall is forecast to cover nearly all of the state on November 6th, but will leave its reddest panhandle counties untouched and chances of precipitation will be highest in the southern half of the Sunshine State, covering the Orlando and Miami areas where the heaviest concentration of Democratic-leaning voters reside.

Though Indiana and Washington state will be untouched by the Hurricane Sandy effect on election results, the election day precipitation forecast could give Mitt Romney and Republican Senate candidates a boost in these states, with high chances of precipitation over Indiana's blue northwestern counties and the entire state of Washington, where the odds of precipitation are extremely high over the western half of the state, covering Washington's most densely-populated and bluest counties.

Precipitation is also likely for the entire swing state of Michigan, where Mitt Romney just closed the polling gap to within a margin of error, trailing President Obama by only 2.7 percent.

In all, Hurricane Sandy and Election Day precipitation are likely to decrease voter turnout with Democratic candidates most heavily affected by the disruptions and bad weather.