Washington — Rejecting demands that she relinquish power after her party's losses in the midterm elections, House Speaker Nancy Pelosi announced Friday that she will run for minority leader, potentially setting up an ideological battle inside the Democratic caucus.

"I am running for Dem leader," Pelosi, Calif., said in a post on her Twitter account. She said her decision was in part "driven by the urgency of creating jobs" and protecting this year's health-care and Wall Street overhauls.

Many Democrats had hoped Pelosi-a central figure in campaigns that allowed Republicans to capture at least 60 new seats and retake control of the House-would step aside. This would have cleared a path for Majority Leader Steny Hoyer, D-Md., who has support from the party's diminished moderate-to-conservative ranks.

But Pelosi's allies have been quietly approaching fellow Democrats, seeking support for her to continue as the party's leader. After her announcement Friday, Hoyer and Rep. James Clyburn, D-S.C., each signaled their interest in running for the No. 2 post.

Pelosi has no challenger at the moment, making her the clear favorite to win in a caucus that is more liberal after Tuesday's losses. She needs only a bare majority to become minority leader. But frustration with her tough leadership style cuts across all ideological ranks of the caucus, and most insiders expect that she will face some opposition in the secret ballot likely to be held the week of Nov. 15.

On Friday, Republicans were practically giddy at Pelosi's announcement.

"The definition of insanity is doing the same thing over and over again, and expecting a different result," said Ken Spain, spokesman for the National Republican Congressional Committee. "Of course, if House Democrats are willing to sacrifice more of their members in 2012 for the glory of Nancy Pelosi, we are happy to oblige them."

Liberal groups lined up behind Pelosi, arguing the Democrats should not view the outcome of the midterms as a sign that they should move to the center.

"After Tuesday's elections, some corporate Democrats are taking the wrong lesson - saying that Democrats should be less progressive and more like the Republicans," the liberal group MoveOn.org said in a letter to its members. "And they're pushing Speaker Pelosi to step down. This would be a terrible loss for progressives, and for the country."

Pelosi's announcement came as a growing - but still small - number of Democrats said she should not continue as leader.

"I'm a big fan of her and would support her choice if she wanted to be minority leader," said Rep. John Yarmuth, D-Ky. "But my perception of what the minority leader does is communications, and I don't think that's her skill set. If that's the major role of the minority leader, I think Steny would be a better choice."

Rep. Dan Boren, D-Okla., one of the few remaining conservative Democrats after several dozen lost Tuesday, told Fox News he cannot "in good conscience support Pelosi" in a leadership election that has still not been scheduled. Rep. Albio Sires, D-N.J., told CQ-Roll Call "we need some new direction, and I think the best way is for her to move on."

Hoyer had said he would not challenge Pelosi. An hour after Pelosi's announcement, Hoyer's office said he would consider a run for minority whip. Clyburn, the majority whip and the highest ranking African American ever in Congress, declared that he will also run for that post.

Many Democrats had hoped to avoid an internal party dispute by rallying the caucus together, but that now appears unlikely. Rep. John Larson, D-Conn.. the No. 4 member in leadership, is running for another term as caucus chairman and likely faces a challenge as well.

After the Twitter announcement, Pelosi issued a more formal statement: "We have no intention of allowing our great achievements to be rolled back. It is my hope that we can work in a bipartisan way to create jobs and strengthen the middle class. Many of our colleagues have called with their recommendations on how to continue our fight for the middle class, and have encouraged me to run for House Democratic Leader. Based on those discussions, and driven by the urgency of protecting health care reform, Wall Street reform, and Social Security and Medicare, I have decided to run."

Pelosi still maintains a great amount of goodwill among colleagues for guiding them to the majority in the 2006 midterms and her aggressive fundraising efforts on their behalf.