Nancy Pelosi spearheaded the Democratic takeover of the US House of Representatives on Tuesday, positioning herself to become the first woman to lead the chamber and President Bush's worst political nightmare.
Democrats also moved to the brink of capturing the Senate, where their final victory could be delayed by a possible recount in Virginia.
House Democratic leader since 2003, the California liberal framed the elections as a referendum on Bush, his unpopular Iraq war and the scandal-rocked, Republican-led House.
"Today the American people voted for change and they voted for Democrats to take our country in a new direction," Pelosi told a victory rally. "That's exactly what we intend to do.
"Mr President, we need a new direction in Iraq," Pelosi said. "Let us work together to find a solution."
Pelosi, 66, appears certain to be elected House speaker by fellow Democrats when the new Congress convenes in January, replacing Dennis Hastert, an Illinois Republican.
Pelosi has said she will not try to end US funding of the Iraq War but will pressure Bush to shift course, begin a phased redeployment of US troops and require Iraqis to take greater responsibility for their own nation.
Pelosi was often ignored or even mocked by Bush during his first six years in office, but the Republican president would have to work with her once she takes the gavel if he expects to get much done in his final two years.
Pelosi has promised to challenge Bush on a host of fronts, from the Iraq war and his tax cuts to education and health care.
She has rejected calls to attempt to impeach Bush and drive him from office but has said Democrats would hold congressional oversight hearings, which could include such matters as whether he manipulated the facts to build early support for the Iraq War.
Democrats rolled up gains of about 30 seats in the House in Tuesday's elections.
They 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.
Virginia Democrat James Webb had an 8,000-vote advantage over Republican Senator George Allen out of more than 2 million cast. A recount could stretch into December, leaving Senate control uncertain.
In Montana, Democrat Jon Tester also held a narrow lead on Republican Senator Conrad Burns, but a final result was not expected until this morninng.
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.
All 435 House seats, 33 of the 100 Senate seats and 36 of the 50 governorships were at stake. Democrats beat Republican Senator Rick Santorum, the third-ranking Republican in the Senate and one of the Democrats' biggest targets this year.
Connecticut Senator 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 Senator Hillary Rodham Clinton sailed to an easy re-election win in New York, setting up a likely 2008 presidential run.
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 Governor Arnold Schwarzenegger rolled to easy re-election.
"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.
Source: China Daily/agencies