President Barack Obama was on a political collision course with his opponents tonight after Republicans made sweeping election gains and vowed to undo some of his major policies.
Top of their agenda was the president's cherished and hard-fought healthcare reforms.
The mid-term voting results delivered a stinging blow to Mr Obama and saw his Democrats lose control of the House of Representatives, although they kept a majority in the Senate..
The result reflected Americans' anxiety about their livelihoods and anger about the economy. The outcome was the House's biggest party turnover in more than 70 years.
Mr Obama now faces the potential for legislative gridlock that could stall his agenda in the final half of his term. Even with the Democrats in control of both chambers of Congress, he spent his first two years battling to pass legislation.
In a news conference tonight Mr Obama took some responsibility for the election thrashing.
He acknowledged that the public was 'deeply frustrated' with the pace of the economic recovery and said one lesson from the results was that he had not made enough progress in creating jobs.
"No one party will be able to dictate where we go from here," he said, a clear warning to Republicans that he won't simply bow to their demands for a sharply conservative switch in economic policy.
And although he said he would listen to Republican ideas to improve the health care system he would not scrap his changes to it.
The first challenge to his plans came just hours after the Republicans' victory was confirmed.
John Boehner, who is due to become the new House leader in January, claimed a voter mandate to roll back the health care overhaul, calling it a "monstrosity."
Trying to do that, however, is likely to prove almost impossible with Democrats still in control of the Senate. Mr Obama also still holds his veto power and the Republicans do not have sufficient numbers to override.
Mr Boehner pledged that Republicans will use their new House majority to seek a "smaller, less costly, and more accountable government." He said he hoped Mr Obama would join them.
The elections were also the biggest test yet of the two-year-old ultra-conservative tea party movement, angered by what it sees as the excessive growth of government. It produced a crop of Republican candidates often at odds with the party establishment, and some of them won key races.
For the Republican Party, there was no historical precedent to guide them in their dealings with these new tea party-backed members of Congress, who were likely to demand radically conservative legislative solutions to the country's problems.
Incomplete returns showed the Republican Party picked up at least 60 House seats and led for four more, far in excess of what was needed for a majority. About two dozen races remained too close to call by early evening European time.
The Republicans' victory eclipsed the 54-seat pickup by the so-called "revolution" that retook the House in 1994 for the first time in 40 years and the 56-seat Republican gain in 1946.
On their night of triumph, Republicans also gained at least six Senate seats
By this afternoon the Republicans had captured 239 House seats and were leading for four more, while Democrats had won 184 and led for eight.
As Mr Obama digested the not-unexpected change in fortunes, he phoned Mr Boehner and Senate Republican Leader Mitch McConnell with congratulations.
Republicans needed to gain 10 seats to take control of the 100-member Senate. By this afternoon Democrats had 51 seats, including two independents, to 46 for Republicans. Three were not yet decided - in Alaska, Colorado and Washington state.
The Republican gains will complicate Mr Obama's ability to enact his proposals during the last two years of his term and possibly force him to fight off attacks on health care legislation and other bills already signed into law.
Although international affairs had little role in the campaign, Mr Obama's global agenda also would be affected in areas such as arms control and climate change.
Before the first results began rolling in, Washington already was buzzing with speculation about whether Republican gains would lead to gridlock or attempts to find common ground, and how they would affect Mr Obama's prospects for re-election in 2012.
Besides the congressional vote, Republicans were making gains in the 37 governors' races at stake Tuesday, capturing at least 11 governorships from Democrats and several state legislatures. Democrats gained four Republican-held governorships - in California, Connecticut, Vermont and Hawaii. The vote count continued in three governors' races that were too close to call.
The new Congress will begin its session in January. Later this month, the current members, including those voted out of office, will go back to work to finish out their terms in what is known as a lame duck session.
While the newly empowered Republicans are likely to want to delay major issues until the new Congress is seated, there are many important measures that are still pending, such as tax cuts set to expire this year and a proposal to reverse the military's ban on openly gay service members.
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