That outcome will strengthen President Barack Obama's hand as he embarks on a second term. Although Republicans apparently have held onto the House of Representatives, the Senate will now provide a liberal counterbalance to a House increasingly dominated by the more stridently conservative voices in the Republican Party.
Just a few months ago, many observers were predicting that Republicans were in position to return to the majority in the Senate. But several key races tightened since then, and as of midnight on Tuesday Republicans had picked up only one new seat, in Nebraska, and had lost at least three, in Maine, Massachusetts and Indiana.
In Massachusetts, progressive icon Elizabeth Warren reclaimed the longtime seat of liberal champion Ted Kennedy, returning to Democrats a seat that freshman Republican Sen. Scott Brown won just two and a half years ago. Democrat Tim Kaine defeated Republican George Allen in a Virginia race pitting two ex-governors against each other. Sen. Sherrod Brown, a Democrat, fended off a well-funded challenge in Ohio, and in Connecticut former wrestling executive Linda McMahon lost to Democratic Rep. Chris Murphy.
Republicans missed some key opportunities. Democrats prevailed in Indiana and Missouri, two races where Republican candidates stumbled badly with insensitive comments about rape. The Indiana race featured Richard Mourdock, who shouldered aside the veteran, respected Republican Sen. Richard Lugar in the primary by running on a farther-right platform and disdaining compromise.
In Maine, independent Angus King won the seat occupied by retiring moderate Republican Sen. Olympia Snowe. Republicans lost another shot at an open seat in Wisconsin, where Rep. Tammy Baldwin became the first openly gay senator in U.S. history, beating out Republican former Gov. Tommy Thompson in the battle for retiring Sen Herb Kohl's seat.
There were still some key wins for Republicans. Rising Tea Party favorite Ted Cruz, who defeated the establishment-anointed candidate in Texas' Republican primary, will represent the Lone Star state. In Nebraska, Republican Deb Fischer rebuffed Democrat Bob Kerrey's attempt to regain a Senate seat he gave up years ago to lead a university in New York. And in Arizona, six-term GOP congressman Jeff Flake defeated Democrat Richard Carmona, a former surgeon general who hoped to appeal to the state's booming Latino electorate.