Fellow Democrats warned that her presence could deter candidates from running in 2012 in an effort to regain the lost ground and could also drive more moderate Democrats toward newly empowered Republicans on legislation, giving them a chance to claim they have bipartisan support.  Ms. Pelosi’s bid to retain her slot also touched off a potentially divisive fight for the No. 2 spot between Representative Steny H. Hoyer of Maryland, a moderate and the second-ranking Democrat now as majority leader, and Representative James E. Clyburn of South Carolina, the No. 3 Democrat and highest-ranking African-American in Congress.  Some Democrats who survived Tuesday’s elections said they would not support Ms. Pelosi’s bid to remain in leadership.  “If we are going to become a nationally significant party again in the House of Representatives, we need a new leader in that position,” said Representative Larry Kissell, Democrat of North Carolina.  Republicans cheered the move, which is likely to mean that Ms. Pelosi and Senator Harry Reid of Nevada, the majority leader, will continue as leaders in their respective chambers despite the party’s midterm election losses.  “My breath is taken away by that announcement,” Michael Steele, the chairman of the Republican National Committee, told reporters when informed of Ms. Pelosi’s decision. “We welcome that.”  A White House spokesman, Bill Burton, said that while the administration did not play a role in leadership contests, the president “appreciates the work of the speaker and the entire House Democratic leadership team who have been great partners in moving the country forward. He looks forward to working with them in the years to come.”  Ms. Pelosi has been secluded in her Capitol office since the election, weighing her options and consulting with allies.  Friday’s decision was aimed at least in part at stemming a quickening revolt among House Democrats who wanted her to step aside. Several lawmakers had gone public with their opposition and many others were privately expressing serious reservations.  “Leaders must know when to play your hand and when to fold,” said Representative G. K. Butterfield, another North Carolina Democrat. “Right now I think it is time for her, for the benefit of her caucus, to take a giant step back.”  But the loss of 60 seats in the election — many of them held by moderates and conservatives — means the makeup of the Democratic caucus in the House will be more liberal in the 112th Congress, making it possible for Ms. Pelosi to retain the position.  Several senior Democrats quickly endorsed Ms. Pelosi after she revealed her intentions via Twitter.  “We need Nancy Pelosi on the field and in this fight for the American people,” said Representative Edward J. Markey, Democrat of Massachusetts.  Ms. Pelosi, who became the first female speaker in history after Democrats captured the majority four years ago, is a prodigious fund-raiser and has collected more than $200 million for the party since joining the leadership in 2002.  She is also a determined political infighter, and both friends and critics said she was being motivated in part by a refusal to be driven from Congress by Republicans. Officials at the Republican National Committee on Friday, happy with the turn of events, changed the sign outside their office to “hire Pelosi” from “fire Pelosi.”  Her decision contrasts with that of J. Dennis Hastert of Illinois, who was the Republican speaker in 2006 when his party lost control. He did not try to stay in leadership, served part of his Congressional term and then resigned. Thomas S. Foley, the speaker when Democrats lost control in 1994, lost his own re-election bid.  But in the past, speakers whose party lost control did sometimes revert to minority leader. Sam Rayburn, a Democrat from Texas, was the last to do so; he twice lost the speakership when his party gave up the majority, serving as minority leader until the House was recaptured.  Allies of Ms. Pelosi argued that if she were the only Democrat to lose her post in the election she would be accepting most of the blame for the defeat. They also argued that ousting her from the post would be was unfair since she had done much of the work of advancing an ambitious Democratic agenda that has also been embraced by President Obama and Mr. Reid.  In her letter to colleagues, Ms. Pelosi made it clear that she intended to resist efforts by the new Republican majority to undo the signature legislative accomplishments of the past two years.  “We have no intention of allowing our great achievements to be rolled back,” she said.  Several lawmakers eager to see Ms. Pelosi step down had indicated support for Mr. Hoyer, but he had repeatedly made it clear that he would not oppose Ms. Pelosi if she chose to try to stay party leader and would instead try to retain his job.  Party elections are to be held the week of Nov. 15 when members of Congress return for a lame-duck session during which Ms. Pelosi will still serve as speaker. Republicans take control of the House in January.  A version of this article appears in print on November 6, 2010, on Page A1 of the New York edition with the headline: Despite Losses, Pelosi Will Run For House Post. Order Reprints| Today's Paper|Subscribe
The speaker’s decision to run for minority leader threatened to fracture a Democratic caucus reeling from election defeat.