In a rout once considered almost inconceivable, Democrats won a 51st seat in the Senate and regained total control of Congress after 12 years of near-domination by the Republican Party. The shift dramatically alters the government's balance of power, leaving President George W. Bush without Republican congressional control to drive his legislative agenda. Democrats hailed the results and issued calls for bipartisanship even as they vowed to investigate administration policies and decisions. Democrats completed their sweep Wednesday evening by ousting Republican Sen. George Allen of Virginia, the last of six Republican incumbents to lose re-election bids in a midterm election marked by deep dissatisfaction with the president and the war in Iraq. Democrats had 229 seats in the House, 11 more than the number necessary to hold the barest of majorities in the 435-member chamber. "In Iraq and here at home, Americans have made clear they are tired of the failures of the last six years," said Sen. Harry Reid of Nevada, the Democrat in line to become Senate Majority leader when Congress reconvenes in January. As watershed elections go, this one rivaled the Republican takeover in 1994, which made Newt Gingrich speaker of the House, the first Republican to run the House since the 1950's President Dwight Eisenhower administration. This time the shift comes in the midst of an unpopular war, a Congress scarred by scandal and just two years from a wide-open presidential contest. Allen lost to Democrat Jim Webb, a former Republican who served as Navy secretary in President Ronald Reagan's administration. A count by The Associated Press showed Webb with 1,172,538 votes and Allen with 1,165,302, a difference of 7,236. Allen was awaiting the result statewide postelection canvass of votes and did not concede the race. Democrats will have nine new senators on their side of the aisle as a result of Tuesday's balloting. Six of them defeated sitting Republican senators from Pennsylvania, Ohio, Missouri, Rhode Island, Montana and Virginia. The other three replaced retiring senators from Maryland, Minnesota and Vermont. Their ideologies are as varied as their home states. Bernie Sanders, an independent who will replace Vermont Sen. Jim Jeffords, is a Socialist who has served in the House and voted with Democrats since 1990. Bob Casey Jr., who defeated Republican Sen. Rick Santorum in Pennsylvania, is an anti-abortion moderate. Webb once declared that the sight of President Clinton returning a Marine's salute infuriated him. Besides the Webb-Allen race, the Montana Senate contest also was too tight to call early Wednesday. But by midday, Democrat Jon Tester outdistanced Republican Sen. Conrad Burns, who had to fight off campaign miscues as well as his ties to Jack Abramoff, the once super-lobbyist caught in an influence-peddling scheme. In the House, 10 races remained too tight to call, with three of them leaning to the Democrats. Rep. Nancy Pelosi, who would become the first female speaker in history, called for harmony and said Democrats would not abuse their new status. She said she would be "the speaker of the House, not the speaker of the Democrats." She said Democrats would aggressively conduct oversight of the administration, but said any talk of impeachment of President Bush "is off the table." In the Senate, Sen. Charles Schumer of New York, the head of the Democrats' Senate campaign committee, said, "We had a tough and partisan election, but the American people and every Democratic senator - and I've spoken to just about all of them - want to work with the president in a bipartisan way."