President George W. Bush cast off his much criticised Defence Secretary Donald Rumsfeld on Wednesday, and took the blame for an election 'thumping' by Democrats he admitted was driven by anger over Iraq.
As Democrats moved to the brink of adding the Senate to their triumphant capture of the House of Representatives in Tuesday's elections, Bush triggered political shock-waves by ditching Rumsfeld, a lynchpin of his administration.
He named former CIA chief Robert Gates at the new Pentagon chief in a move which could herald a course correction in the bloodstained US occupation of Iraq, where 2,800 US troops and tens of thousands of civilians have died.
"I recognise that many Americans voted last night to register their displeasure with the lack of progress being made there," Bush said at a White House news conference.
"After a series of thoughtful conversations, Secretary Rumsfeld and I agreed that the timing is right for new leadership at the Pentagon," Bush said, adding that Rumsfeld, 74, would have left however the elections turned out.
The president was "disappointed" by the Democrat landslide but acknowledged it was whipped up by anger over the troubled US occupation.
"As the head of the Republican Party, I share a large part of the responsibility ... I you look at it race by race, it was close. The cumulative effect, however, was not too close. It was a thumping."
Democrats meanwhile picked up a fifth Senate seat, in Montana, edging close to victory in the powerful upper chamber after grabbing the House of Representatives for the first time since 1994.
Democrat Jon Tester beat incumbent Republican Conrad Burns by fewer than 5,000 votes, according to US networks.
The final and decisive Senate race in Virginia was too close to call, with Democrat challenger Jim Webb leading by 7,000 votes. It could be weeks before
that vote is declared, with a recount possible.
A spokesman for Virginia Senator George Allen would not concede defeat.
Already flexing their new power, Democrats welcomed Rumsfeld's departure.
"For the first time it looks like the president is listening," said Senator Chuck Schumer, architect of the party's surge in the Senate.
Earlier, Nancy Pelosi, set to become the first woman speaker of the House, had called for Rumsfeld to go. Bush's defeated Democrat opponent in the 2004 presidential John Kerry said the move was "overdue."
Rumsfeld's departure put the capped a remarkable career of a political bruiser who served twice as Pentagon chief, and was White House chief of staff to president Gerald Ford, after starting out as a navy pilot.
But he will likely go down in history as the man who led US troops into a quagmire in Iraq, from which their seem few acceptable exit strategies.
Pentagon spokesman Bryan Whitman said Rumsfeld gave no indications in staff meetings on Wednesday he was ready to leave.
Former US spy chief Gates, 63, has served six US presidents, including the current US leader's father George Bush.
Significantly, he is a member of the bipartisan Iraq Study Group under former Republican secretary of state James Baker tasked with examining new US approaches on Iraq which is due to report to Bush within a few months.
The Republican drubbing means Bush is already certain to face new scrutiny over Iraq and a difficult two final years in the White House.
The opposition party beat most predictions by picking up nearly 30 seats to take control of the 435-member House for the first time since 1994.
Republican House Majority Leader John Boehner said his party was "deeply disappointed" but predicted it would reclaim a majority in 2008.
Voters piled on anger over the course of the war in Iraq and a heap of corruption and scandals which have tainted the Republicans in the past two years, exit polls suggested.
They also expressed concern over skyrocketing health care costs, the economy, illegal immigration and "values" issues such as stem-cell research, gay marriage and abortion.
Republican incumbents crashing to defeat in Arizona, Connecticut, Florida, Indiana, Iowa, Kansas, Kentucky, Minnesota, Missouri, New Hampshire, New York, North Carolina, Ohio, Pennsylvania, Rhode Island and Texas.
The Democrats also won six governors' seats to take the majority of statehouses for the first time in 12 years. Hollywood star Arnold Schwarzenegger, a Republican, bucked the trend and was re-elected in California, crushing Democratic rival Phil Angelides.
Democrat Keith Ellison, from Minnesota, became the first Muslim elected to Congress, and Hillary Clinton easily beat her Republican rival to claim a second Senate term, further spurring expectations of a 2008 presidential run.
In other Senate races, Democratic challenger Claire McCaskill toppled Republican incumbent Senator Jim Talent in Missouri, and Democrat Bob Casey Jr. ousted conservative Senator Rick Santorum in Pennsylvania.
Democrat Sherrod Brown defeated Republican Senator Mike DeWine in Ohio, and Democrat Sheldon Whitehouse beat Republican incumbent Lincoln Chafee in Rhode Island.