Democratic senate candidate and former Virginia Gov. Timothy Kaine celebrates his win over Republican George Allen during his victory party in Richmond, Va., Wednesday, Nov. 7, 2012. 

Steve Helber/AP

Democratic Sen. Sherrod Brown, left, is hugged by his daughter, Liz, as they celebrate at the Ohio Democratic party election night celebration Tuesday, Nov. 6, 2012, in Columbus, Ohio. Brown defeated GOP challenger Josh Mandel, the state treasurer. (AP Photo/Tony Dejak)

Democrat Joe Donnelly thanks supporters after winning the U.S. Senate seat over Republican Richard Mourdock at an election night celebration in Indianapolis, Tuesday, Nov. 6, 2012. Donnelly triumphed in one of the nation's most tumultuous Senate races, capitalizing on fallout over his tea party-backed opponent's comment that a pregnancy resulting from rape is "something God intended" to capture a seat that just a year ago looked to be a lock for Republican U.S. Sen. Richard Lugar. (AP Photo/Michael Conroy)

Independent Angus King celebrates his victory for the U.S. Senate seat vacated by Olympia Snowe, R-Maine, Tuesday, Nov. 6, 2012, in Freeport, Maine. (AP Photo/Robert F. Bukaty)

U.S. Sen. Scott Brown, R-Mass., gets into his truck after voting in Wrentham, Mass., on Election Day, Tuesday, Nov. 6, 2012. Brown is facing Democratic candidate Elizabeth Warren for the U.S. Senate. (AP Photo/Gretchen Ertl)

Democratic candidate for U.S. Senate Elizabeth Warren, left, emerges from the polling booth as she votes in Cambridge, Mass. on Election Day, Tuesday, Nov. 6, 2012. Warren is running against Sen. Scott Brown (R-MA), who was elected in a special election in 2010 after the death of Sen. Ted Kennedy (D-MA). (AP Photo/Josh Reynolds)

U.S. Sen. Claire McCaskill, D-Mo., votes at her polling place, Kirkwood Community Center, Tuesday, Nov. 6, 2012, in Kirkwood, Mo. McCaskill is running for reelection against Republican challenger Rep. Todd Akin, R-Mo. (AP Photo/Jeff Roberson)

Missouri U.S. Senate candidate, Rep. Todd Akin, R-Mo., votes at his polling place, Star Bridge Christian Center, Tuesday, Nov. 6, 2012, in Wildwood, Mo. Akin is running against incumbent Sen. Claire McCaskill, D-Mo. (AP Photo/Jeff Roberson)

Republican Richard Mourdock, a candidate for Indiana's U.S. Senate seat, greets voters and supports outside a polling place in Indianapolis, Tuesday, Nov. 6, 2012. Mourdock is running against Democrat Joe Donnelly. (AP Photo/Michael Conroy)

Joe Donnelly, Indiana Democratic candidate for U.S. Senate, casts his vote Tuesday Nov. 6, 2012 in South Bend, Ind. Donnelly is running for the Senate seat that was held by Republican Richard Lugar who lost in the primary to Richard Murdock. (AP Photo/Joe Raymond)