Voting Begins in Crucial US Midterm Election

First lady Michelle Obama and Maryland Democratic gubernatorial candidate, Lt. Gov. Anthony Brown, walk together on stage during a Get Out the Vote rally, Baltimore, Maryland, Nov. 3, 2014.

Diego Valencia processes Oregon ballots at Multnomah County election headquarters in Portland, Oregon, Nov. 3, 2014.

Republican House candidate Barbara Comstock (center) before speaking at a Get Out the Vote rally campaign in Sterling, Virginia, Nov. 3, 2014.

American singer and songwriter Prince performs on the Isle of Amager in Copenhagen, Denmark, Aug. 6, 2011.

Jill Biden (right), wife of Vice President Joe Biden, campaigns with Sen. Mark Udall, D-CO (third from right) and Sen. Michael Bennet, D-CO (second from right), in Boulder, Colorado, Nov. 1, 2014.

Hillary Rodham Clinton (right) reacts as she is introduced by Sen. Jeanne Shaheen, D-NH (far left) and Gov. Maggie Hassan, (D-NH) during a Get Out the Vote rally center, Nashua, NH, Nov. 2, 2014.

Election judge Kathryn Ballen (right) takes a ballot from a driver as motorists proceed through a drive-up lane for ballot drop off in the parking lot of Harvard Gulch Recreation Center in south Denver, Colorado, Oct. 31, 2014.