Dems retain majority in Senate

Democrats are assured of retaining their U.S. Senate majority after Republicans lost seats in Indiana, Massachusetts and Maine, and Democrats held on to crucial seats in Virginia and Missouri.

In Virginia, Democrat Tim Kaine beat Republican George Allen in a race that has mirrored the presidential campaign in polls. Allen lost the Senate seat six years ago to Democrat Jim Webb, who is retiring after one term.

Indiana Democrat Joe Donnelly, a congressman, defeated Republican Richard Mourdock, who in May ousted six-term incumbent Richard Lugar in a primary vote. Massachusetts Sen. Scott Brown lost to Democrat Elizabeth Warren.

"We have defied the odds, we have won the night, and we will have a Democratic majority," Sen. Patty Murray of Washington, who heads Senate Democrats' campaign efforts, told supporters .

Democrats control the Senate 53-47. Republicans needed to pick up four net seats to gain a majority. The electoral landscape was supposed to favor Republicans, who were defending 10 seats compared with 23 Democratic seats on the ballot this year.

Scott Brown, who won the late Massachusetts Sen. Edward Kennedy's seat in a 2010 special election, told supporters after his defeat by Warren, "May she bring that Senate office great credit, just as I set out to do nearly three years ago."

In Maine, independent Angus King beat a Republican and a Democrat for the seat being vacated by Republican Sen. Olympia Snowe, whose decision in February to retire was a blow to Republicans' hopes of gaining Senate control.

King is expected to caucus with Democrats.

Missouri Sen. Claire McCaskill, a Democrat once considered the party's most vulnerable in the chamber, held off a challenge by Akin.