Four years ago George Bush and his political strategist Karl Rove ensured mid-term victory for the Republicans by framing the contest as a referendum on the then popular President. This time the election was again a referendum on the President and it was his unpopularity over the war in Iraq that caused his party to lose so badly - his first defeat since a failed bid for Congress in 1978.
The Democrats may have worked hard to raise millions of dollars, to find electable candidates and to build their organisation across the nation, but of far more significance, say they experts, was Mr Bush's unpopularity and that of the Republican-controlled Congress.
"This is one of those moments that come along once in a decade in American politics when the public says, 'We're mad as hell, we're not going to take it and we want something different'," said Thomas Mann, an elections expert at the Brookings Institution.
"The strategies of Rove and the Democratic alternatives pale in comparison to the fact that things are going really bad in Iraq. It's far more the governance of Bush and the Republican Congress that provided the opportunity for this shift in American politics."
That is not to say the Democrats simply stood back and watched the Republicans implode. Rahm Emanuel, the Illinois congressman who chaired the House campaign committee, and Charles Schumer, his Senate counterpart, worked ferociously to raise funds to match the Republicans spending. As a result, in the final days of the campaign, Mr Schumer was able to direct millions of dollars for advertising in places such as Maryland and New Jersey where the races were surprisingly tight.
Likewise they devoted energy to finding voter- attractive, moderate candidates such as Heath Shuler, a former quarterback with the Washington Redskins American football team who won a House race in North Carolina.
Republicans also lost heavily in normally solid Indiana to candidates who positioned themselves as moderates or even conservative.
Across the nation the Democrats have also been helped by Chairman Howard Dean's efforts to build grassroots support and organisation, something that will probably have even greater impact in 2008 when the party will try to fight a 50-state presidential election campaign.
Both polls and anecdotal evidence suggested that while factors such as get-out-the-vote initiatives may have played a role in some close races, it was overwhelmingly antipathy towards Mr Bush and a war that has cost the lives of more than 2,800 US troops and perhaps 655,000 Iraqis that drove swing voters and independents to plump for the Democrats.
"It's both - the Democrats won it and the Republicans lost it," said Larry Sabato, professor of politics at the University of Virginia. "It was a classic sixth year election, it was a six-year itch."
From the perspective of the Republicans the news in the run-up to the election could not have been worse - from the lobbying scandal that led to the conviction of Republican Congressman Bob Ney of Ohio, to the sexual scandal surrounding Congressman Mark Foley, whose Florida seat was captured by the Democrats to the constant news of carnage and chaos from Iraq.
Many Republican candidates sought to distance themselves from Mr Bush and his Iraq policy but some were not able to run fast enough.
Terry Mcauliffe, the former chairman of the Demo-crats who four years ago complimented Mr Bush over the Republican victory, said that in 2002 the Republicans had used the "war on terror" to attack the Democrats.
"I think the Democrats should have fought harder - something John Kerry should have done with the Swift Boats. You need to hit them back," he said.
Unlike in 2002 when President Bush carried many candidates to power on his coat-tails, this time he was kept to the margins of the campaign and used mainly to raise money. Over 20 months he managed to raise $193m. It was a lot, but not enough.Reuse content