JOIN USTwo years after Obama won the White House, voter anxiety about the economy and discontent with his leadership fueled big Republican gains that toppled Democratic House Speaker Nancy Pelosi from power and are likely to slam the brakes on Obama's agenda.
Television networks projected Republicans would pick up at least 50 House seats, far more than the 39 they needed for a majority that would elevate conservative John Boehner to House speaker. It was the biggest shift in power since the 1994 Republican landslide gave them a 54-seat gain.
Republican control of even one chamber of Congress would likely spark legislative gridlock, weakening Obama's hand in fights over the extension of soon-to-expire income-tax cuts and the passage of comprehensive energy or immigration bills.
"We have come to take our government back," Republican Tea Party favorite Rand Paul, who won a Senate race in Kentucky, told supporters.
The Republicans' expected gains drove stocks higher on Tuesday on hopes of a more conservative and business-friendly Congress.
In the Senate, Democrats held the late Robert Byrd's seat in West Virginia and appeared likely to retain at least a narrow Senate majority. Republicans picked up three Democratic seats, but still needed to sweep six crucial toss-up Senate races, including those in Democratic-leaning California and Washington, to seize control.
All 435 House seats, 37 of the 100 Senate seats, and 37 of the 50 state governorships are at stake in Tuesday's voting.
Obama swept into office two years ago with hopes he could lead the United States out of a deep economic crisis, but persistent high unemployment and a gaping budget deficit turned many voters against him and his fellow Democrats, who passed a costly economic stimulus package, industry bailouts and healthcare and financial regulatory reforms.
In the Senate, Republicans picked up Senate seats from Democrats in Indiana, North Dakota and Arkansas, where they bumped off Senator Blanche Lincoln. They also held their Senate seats in Ohio and New Hampshire.
Florida Republican Marco Rubio and Kentucky Republican Rand Paul became the first Tea Party-backed candidates to win Senate seats, ensuring an influx of conservative views in the staid chamber. Another Tea Party favorite, Republican Christine O'Donnell in Delaware, lost her race.
TEA PARTY RISES
Anger over government spending and economic weakness gave rise to the Tea Party, a loosely organized conservative movement that backs smaller government and lower taxes.
Television networks reported their exit polls showed voters were deeply worried about the economy, with eight in every 10 voters saying it was a chief concern, and unhappy with Obama. Four of every 10 voters said they supported the Tea Party.
"The newly elected crop of House and Senate Republicans will see their mission as not to compromise and cut deals with President Obama, but rather to destroy his remaining agenda and undo healthcare and financial services reform," said Ethan Siegal, an analyst with the Washington Exchange, a public policy advisory group.
Obama will hold a news conference at 1 p.m. EDT (1700 GMT) on Wednesday to talk about the post-election landscape.
Republican candidates have pushed an agenda of spending cuts and at least a partial repeal of Obama's healthcare and Wall Street reforms, but Obama could veto their efforts.
Some research suggests that stocks languish when power is split in Washington, but they have risen in recent months on the promise of a more business-friendly Congress.
That trend continued on Tuesday, with the greatest gains in sectors expected to benefit from a shift in power, though many forecast a sell-off in the days ahead. Health insurer stocks rose, with an index of the sector gaining 2.7 percent as investors bet that Obama will have to battle to keep his healthcare reform in place.
Voters on Tuesday also weighed in on a variety of topics: in California, for example, they could approve a measure that would legalize possession of marijuana.
In perhaps the country's most high-profile race, Senate Democratic leader Harry Reid is embroiled in a neck-and-neck re-election fight with Tea Party favorite Sharron Angle in Nevada. The race could hinge on how many voters pick the "none of the above" option on the Nevada ballot.