Rep. Shelley Berkley, D-Nev. heads to an early voting location to vote, Thursday, Oct. 25, 2012, in Las Vegas. Interest in this year's election is being driven by races between President Barack Obama and Mitt Romney, and U.S. Sen. Dean Heller, R-Nev., and his Democratic challenger, Berkley. (AP Photo/Julie Jacobson)

Photo by: Julie Jacobson

Rep. Shelley Berkley, D-Nev. heads to an early voting location to vote, Thursday, Oct. 25, 2012, in Las Vegas. Interest in this year's election is being driven by races between President Barack Obama and Mitt Romney, and U.S. Sen. Dean Heller, R-Nev., and his Democratic challenger, Berkley. (AP Photo/Julie Jacobson)