As the race continued to Pennsylvania, Indiana, and North Carolina, many observers concluded that Clinton had little chance to overcome Obama's lead in pledged delegates. Even if she were to succeed in changing the dynamics of the race, there would not be enough pledged delegates remaining for her to catch up under most realistic scenarios. Some analysts believed Clinton could still win the nomination by raising doubts about Obama's electability, fighting for Michigan and Florida delegates to be seated at the convention, and convincing superdelegates to support her despite her expected loss in the pledged delegate vote. However, the window of opportunity for re-votes in Michigan and Florida appeared to close in late March, and House Speaker Nancy Pelosi, chairwoman of the Democratic National Convention, said that it would be harmful to the party if superdelegates were to overturn the result of the pledged delegate vote.