Outgoing House Speaker Nancy Pelosi, facing a growing rebellion against her bid to become minority leader, is likely to be challenged for the post by a moderate Democrat.

North Carolina Rep. Heath Shuler, who has been sending signals since last month that he would run against the San Francisco liberal if she didn't step aside, is expected to launch his leadership bid on Sunday when he appears on CNN's "State of the Union." He's also appearing on MSNBC's "Morning Joe" on Monday.

Shuler, a former NFL quarterback, told the Clay County Progress this week that he had no choice but to leave the sidelines.

"At this point, no one has come forward, no one in leadership for a long time," Shuler told the North Carolina weekly newspaper. "It will be very tough. It is probably a race we can't win. But we need a moderate voice in the Democratic Party."

Shuler's spokeswoman did not respond to an e-mail seeking comment. Neither did Pelosi's office.

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The challenge comes as House Democrats just avoided a messy leadership struggle between Reps. Steny Hoyer of Maryland and James Clyburn of South Carolina for the No. 2 post of their new minority. Pelosi brokered a deal that will allow Hoyer to become second in command while Clyburn receives a new position that will be labeled the third-ranking post in leadership.

But several Democrats, most of them moderates from conservative districts, have made clear that they won't support Pelosi's leadership bid after their party suffered historic losses to Republicans last week. 

Democrats lost more than 60 seats, with a few races still up in the air. Many of the defeats came in conservative or swing districts and many of her critics are lawmakers who barely survived.

Party elections, which occurs behind closed doors, are scheduled for Wednesday.

Pelosi's quick postelection announcement that she would run for minority leader startled many Democrats.

Rep. Dan Boren of Oklahoma told Fox News last week that voters sent a message that they want the Democratic Party to move in a new direction.

"They want someone to lead the party who is going to be bipartisan," he said. "This is very disappointing for a lot of us in the center."

Pelosi told NPR on Friday that she decided to run so she can finish what she started.

"My motivation for running is to be in the strongest possible position to create jobs, to continue the work we did in the previous administration, to preserve Social Security, to protect what we did for health care reform and Wall Street reform," she told the network.

She also blamed the high unemployment rate for last week's election results.

"We didn't lose the election because of me," she said, adding that she believes she has been widely attacked because of her effectiveness as speaker.

"The reason they had to try to take me down is because I've been effective in fighting the special interests in Washington, D.C.," she said.

On Friday, 31 female House Democrats, including two members-elect, endorsed Pelosi for minority leader in an open letter.

"As the first woman Speaker of the House, Nancy Pelosi has borne the brunt of unfair criticism and attacks, but her record of accomplishment speaks for itself – particularly to women," the letter reads, citing her record-high promotions of women into committee chairmanships, among other things.

"At a time when the incoming Majority is expected to threaten the progress we have made for women and families, we need Nancy Pelosi as Democratic Leader to help us stay unified and fight back," the letter says.

But even some longtime supporters of Pelosi have said she needs to step aside as the party leader.

"I voted for everything she asked me to vote for," said Rep. Albio Sires, D-N.J. "You know, sometimes in this business it's difficult to know when to move on."

"With all the losses that we had with governors and all the redistricting that's going to be done, we don't need the target," Sires said, referring to the once-a-decade House redistricting process about to begin nationwide.