WASHINGTON - Less than two months after voters gave Republicans six more Senate seats and control of the House, the GOP is lining up candidates for 2012, well ahead of the pace of previous election cycles.

Looking to ride what they hope will be a continuing Republican wave, nine potential challengers, including two each in Missouri and Virginia, already have said they are weighing bids for the U.S. Senate.

They have an abundance of targets. Twenty-one of the 33 Senate seats up in 2012 are held by Democrats and two others are occupied by independents who align themselves with Democrats. Including those independents, Democrats will hold a 53-47 Senate advantage in the new Congress that convenes Jan. 5. The 10 Republican senators up for re-election in 2012 have yet to draw a challenger.

"I want to do my part in fighting for America's future. That's why I have decided to run for the United States Senate," Republican Sarah Steelman said in announcing her challenge to Missouri Democratic Sen. Claire McCaskill.

Former Sen. Jim Talent, too, is weighing a rematch against McCaskill. The two faced off in 2006 and McCaskill won in that Democratic wave.

Florida Senate President Mike Haridopolos has visited Washington to talk about his expected Senate bid against Democratic Sen. Bill Nelson, who won a second term with 60 percent of the vote in 2006. George LeMieux, who filled the last 15 months of Republican Mel Martinez' term through an appointment, might also seek Nelson's seat.

LeMieux is returning to Florida to make room for Marco Rubio, a former speaker of the Florida state House who won election to the Senate this year.

Democratic Sen. Ben Nelson of Nebraska, who won by 28 percentage points four years ago, drew an early challenger in state attorney general Jon Bruning just days after last month's election.

In Montana, first-term Democratic Sen. Jon Tester has drawn GOP businessman Steve Daines as a challenger. Republican Marc Scaringi has announced a campaign against Democratic Sen. Bob Casey of Pennsylvania, another 2006 winner expected to face a tough re-election bid.

"That's really a reflection of the opportunity people see," said Sen. John Cornyn, the Texas Republican who heads the GOP Senate campaign.

In an interview, Corynyn recalled having a hard time finding Republicans willing to challenge Senate Democrats after President Barack Obama's landslide in 2008.

The collapse of Obama's sky-high popularity was a major factor, Cornyn acknowledged. In February 2009, Obama had a 67 percent approval rating in an AP-GfK poll. The weekend after November election, the same poll found Obama had 47 percent approval to 51 percent disapproval.

"When we went into the campaign in January 2009, it looked one way," Cornyn said. "By November 2010, it changed dramatically."

Democrats find themselves having to defend so many seats because of their success in 2006, when they picked up six seats in the Senate and also took the House away from Republicans after a dozen years of GOP control.

"This is the compensation we have for being beaten very badly in 2006," Cornyn said. "We're glad to be in this posture. I'd rather be in our position than theirs."

In Virginia, Democratic Sen. Jim Webb could face a rematch against former Sen. George Allen. Webb inched out Allen in 2006, but Allen has been building buzz for a return to Washington with speeches to tea party groups and less-than-subtle hints he is weighing another campaign.

Allen also might not be alone seeking the nomination. Prince William Chairman Corey Stewart has floated the idea of a campaign for Senate and took a swipe at Allen in the process.

"Sen. Allen was a great governor of Virginia, he really was," Stewart, a Republican, said on a local TV interview. "But his record in the United States Senate was mediocre. And I don't think most people in Virginia think of him as a great United States senator. They think of him as a great governor."

Indeed, contested primary races could again be an issue for Republicans in 2012, just as they were in 2010, when Democrats retained a couple of Senate seats after candidates who were viewed as their most potent GOP challengers lost their party's primary.