Republicans, including candidates with support from the conservative Tea Party movement, have scored early victories in U.S. congressional elections.
Republican Rand Paul, who had enthusiastic Tea Party support, was one of the early winners in the Tuesday election.
The first-time candidate defeated Democrat Jack Conway to win a senate seat in Kentucky.
He campaigned against budget deficits and President Barack Obama's economic stimulus and health care overhaul programs.
During the campaign, his opponent Conway, the state's attorney general, said Paul was too extreme.
Another Tea Party favorite, Senator Jim DeMint from South Carolina, won a second Senate term.
The tea party is a grassroots, conservative, anti-spending movement which has gained momentum within the Republican party over the last two years.
But one of the other Tea Party candidates, Christine O'Donnell, lost in the Senate race in Delaware, defeated by Democrat Chris Coons.
Early results indicated Republicans could be on their way to gaining a majority in the House of Representatives, but would have to win a lot of difficult races to also gain control of the Senate. Both legislative bodies are currently dominated by Mr. Obama's Democratic Party.
The current lower House speaker, Democrat Nancy Pelosi, made a plea to voters, as polls were still open in many states.
"We have taken the country in a new direction," she said. "We are not going back to the failed policies of the past. We are fighting for the middle class. Thank you for being part of that fight."
Mr. Obama spoke on several urban radio stations Tuesday, urging voters to keep Democrats in command of Congress, as they have been since he was elected president in 2008.
But exit polls indicated that with unemployment close to 10 percent, more than 60 percent of voters said they felt the country was going in the wrong direction.
Note: Vertical line represents number needed for majority (218).
Note: Vertical line represents number needed for majority (51).