Democrats swept Republicans from power in the US House of Representatives and moved to the brink of capturing the Senate, where their final victory could be delayed by a possible recount in Virginia.
Democrats rolled up gains of about 30 seats in the House in Tuesday's elections, riding to a huge victory on a wave of public discontent with the Iraq war, corruption and Republican President George W. Bush's leadership.
In a harsh setback to Bush and Republicans, Democrats picked up four of the six Senate seats they needed for a majority and led in races for the other two, in Montana and Virginia, threatening to take control of both chambers of Congress for the first time in 12 years.
A potential recount and possible legal challenges in Virginia could delay the final result, dredging up memories of the 2000 presidential election recount that lasted five weeks.
Virginia Democrat James Webb had an 8,000-vote advantage over Republican Sen. George Allen out of more than 2 million cast. A potential recount could stretch into December, leaving Senate control uncertain.
In Montana, Democrat Jon Tester also held a narrow lead on Republican Sen. Conrad Burns, but a final result was not expected until later on Wednesday.
The narrow governing majorities in Congress, especially the Senate, were almost certain to spawn more partisan gridlock and political warfare during Bush's final two years in the White House.
Bush scheduled a news conference for 1 p.m. EST (1800 GMT) to discuss the results.
Democratic control of the House will make outspoken liberal Rep. Nancy Pelosi the first female speaker and could slam the brakes on much of Bush's agenda and increase pressure for a change of course in Iraq.
"Tonight is a great victory for the American people," Pelosi told a Democratic rally on Capitol Hill. "Today the American people voted for change, and they voted for Democrats to take our country in a new direction."
All 435 House seats, 33 of the 100 Senate seats and 36 of the 50 governorships were at stake. Democrats beat Republican Sen. Rick Santorum, the third-ranking Republican in the Senate and one of the Democrats' biggest targets this year.
Connecticut Sen. Joseph Lieberman, running as an independent, beat Democratic anti-war challenger Ned Lamont, who had defeated the former vice presidential nominee in the Democratic primary.
Democratic Sen. Hillary Rodham Clinton sailed to an easy re-election win in New York, setting up a likely 2008 presidential run.
"This is a wake-up call to the Republican Party," said Republican Sen. John McCain of Arizona on CNN.
DEMOCRATIC GOVERNORS WIN BIG
Democrats also scored big wins in governors' races, taking six seats from Republicans and winning a national majority that could give them an edge in the 2008 presidential election. California Gov. Arnold Schwarzenegger rolled to easy re-election.
The Democratic sweep in the House reached deep into Republican bastions like Indiana, where three incumbents lost, and Kansas, where incumbent Rep. Jim Ryun was defeated.
"We're finally beginning to become a national party again after 12 years," said Democratic Party chief Howard Dean, who has worked to build up party operations in all 50 states.
The Democratic victory gives the party control of House legislative committees that could investigate the Bush administration's most controversial decisions on foreign, military and energy policy.
Democrats have promised votes on much of their agenda within the first 100 hours of taking House power, including new ethics rules, a rise in the minimum wage, reduced subsidies to the oil industry and improvements in border and port security.
Early exit polls showed voters disapproved of the war in Iraq by a large margin, but voters said corruption and ethics were more important to their vote, CNN said.
Democrats hammered Republicans for spawning a "culture of corruption" in Washington, with four Republican House members resigning this year under an ethics cloud.
The party was hit by allegations about influence peddling, links to convicted lobbyists and a Capitol Hill sex scandal involving Republican Rep. Mark Foley's lewd messages to teenage male congressional assistants.
The campaign-trail debate was dominated by Iraq, and Bush defended his handling of the war to the end despite job approval ratings mired in the mid-30s. He questioned what Democrats would do differently and predicted Republicans would retain control of Congress.
History was with the Democrats -- the party holding the White House traditionally loses seats in a president's sixth year.