Republicans seized control of the House of Representatives in a piercing rebuke to President Barack Obama, scoring the chamber's biggest party turnover in more than 70 years. Democrats lost ground in the Senate, but kept their majority, vote tallies showed Wednesday.
Obama now faces the potential for legislative gridlock that could stymie his agenda in the final half of his term. Even with his Democrats in control of both chambers of Congress, he spent his first two years battling to pass legislation.
The stinging blow to Obama and his Democrats reflected Americans' anxiety about their livelihoods and anger about the economy, where unemployment remains stuck near 10 percent.
The elections were also the biggest test yet of the two-year-old ultraconservative 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. 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 _ among them were tea party favorites Rand Paul in Kentucky, Mike Lee in Utah and Marco Rubio in Florida.
All 435 seats in the House were on Tuesday's ballot, plus 37 in the Senate. Also, 37 states chose governors.
By midmorning Wednesday, the Republicans had captured 239 House seats and were leading for four more, while Democrats had won 184 and led for eight.
Republican John Boehner, destined to replace Nancy Pelosi as House speaker, called the results "a repudiation of Washington, a repudiation of big government and a repudiation of politicians who refuse to listen to the people."
By Wednesday morning, Boehner was claiming a voter mandate to roll back the Obama administration's health care overhaul, calling it a "monstrosity." Trying to do that was likely to prove futile with Democrats still in control of the Senate and unlikely to allow such a measure to reach the floor for debate or vote.
Obama also still holds his veto power and the Republicans do not have sufficient numbers to override.
As Obama digested the not-unexpected change in fortunes, he telephoned Boehner and Senate Republican Leader Mitch McConnell with congratulations.
The Republican leaders scheduled a late-morning news conference, to be followed a short while later by Obama's own meeting with reporters at the White House.
At the White House the morning after, senior Obama aides were noticeably absent from TV shows, where they normally appear after major events to put their spin on developments. All morning long, administration officials were staying silent so that Obama himself would have the first say.
In the Senate, Republicans won at least six seats now held by Democrats. Among them was Obama's old seat in Illinois, captured by a congressman, Rep. Mark Kirk.
But Democrats won one of the most-closely watched races, with Senate Majority Leader Harry Reid defeating Sharron Angle, a favorite of the tea party movement. Democrats also retained seats targeted by Republicans in West Virginia and California, where liberal incumbent Barbara Boxer defeated former Hewlett-Packard chief executive Carly Fiorina.
Republicans needed to gain 10 seats to take control of the 100-member Senate. As of early Wednesday, Democrats had 51 seats, including two independents, to 46 for Republicans. Three races were not yet decided _ in Alaska, Colorado and Washington state.
The Republican gains will complicate 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, 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 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 10 governorships from Democrats and several state legislatures. Democrats gained two Republican-held governorships _ in California and Hawaii. The vote count continued in five governors' races that were too close to call.
The Democrats picked up one governor's mansion when Vermont's Republican gubernatorial candidate Brian Dubie conceded the race to his Democratic opponent Peter Shumlin. The gubernatorial races were especially important as states conduct the once-a-decade post-census task of redrawing congressional districts.
In the Senate, tea-party backed candidate Cuban-American Marco Rubio, a Cuban-American, won in a three-way race in Florida. Nikki Haley, an Indian-American, won the South Carolina governorship.
But the tea party may have cost Republicans two Senate seats. Republicans were favored to win Vice President Joe Biden's former seat in Delaware, until tea party-backed Christine O'Donnell defeated a moderate veteran congressman in the primary. O'Donnell, whose outlandish remarks won her national attention, was defeated by Democrat Chris Coons.
Among the Senate races yet to be called was one in Alaska, where Joe Miller, a candidate supported by the tea party and former Gov. Sarah Palin, faces a strong write-in challenge from the incumbent he defeated in the Republican primary, Lisa Murkowski. Democrat Scott McAdams is trailing in third place. The two other races, in Washington state and Colorado, remain 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 will likely 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 servicemembers.
One big foreign policy issue that is pending is the new START treaty signed by Obama and Russian President Dmitry Medvedev in April. It calls for big cuts in nuclear arms and would replace a similar treaty that expired last year. The Senate must ratify the treaty with 67 votes. The Russians have said ratification is a key to the success of Obama's desire to reset relations with Moscow, which deteriorated badly under former President George W. Bush.