One day before Election Day, more than 30 million people have already voted across the country, according to data complied by George Mason University's United States Elections Project.

The votes have been cast by mail or in person across 34 states and the District of Columbia, the Associated Press reported.

Of five battleground states that report partisan turnout, Democrats are leading in four, according to the George Mason project. States don't tally votes until Election Day, however.

CBS News reported that in 2008, some polling experts said they knew the winner a week before the election due to early voting results. But this year, CBS reported that the race is closer and that Republicans are relying more heavily on Election Day turnout.