In much-watched Nevada, the sun will rise on Election Day with most votes already cast.

This year, more than 700,000 of the state's roughly one million expected voters have already weighed in at the ballot box, according to state figures released over the weekend. That's a record high, said David Damore, an associate professor of political science at University of Nevada, Las Vegas, who studies campaigns and elections.

How the vote will break down is not clear yet, but the state released the party affiliations of those who voted, and Democrats had a large lead -- 70,000 -- in populous Clark County, where Las Vegas is located.

Still, Damore says a more telling political indicator may be the numbers from Washoe County, where Reno is located. Republicans and Democrats were neck-and-neck there -- which amps up pressure on the GOP for election day.

Now, Damore said, Romney needs a "huge" Republican turnout statewide, a strong Republican showing from independent voters and a poor turnout from Democrats. In Nevada, he said, "Romney needs a miracle."