Clinton urges backers to ignore calls for her to quit

Clinton's campaign, however, insisted she was in the race until at least June 3, when the last primaries are held. At a rally under the dome of the West Virginia Capitol, Clinton argued that her coalition is the stronger one for November.

"We need to bring back hard-working people to the Democratic Party," she said. "I'm winning Catholic voters and Hispanic voters, blue-collar workers and seniors - people Senator McCain will need in the general election."

She made a similar point, but in a more provocative way, in an interview published yesterday in USA Today that generated buzz in the liberal blogosphere and among some political commentators who said Clinton was playing the race card. She said news reports on the Indiana and North Carolina primaries on Tuesday have "found how Senator Obama's support among working, hard-working Americans, white Americans, is weakening again, and how whites in both states who had not completed college were supporting me."

She was also scheduled to campaign yesterday in Oregon, which votes May 20, and South Dakota, which votes June 3.

Instead of visiting any primary states yesterday, Obama was in Washington. On the House floor, he was quickly surrounded by well-wishers calling him "Mr. President" and reaching out to pat him on the back or shake his hand. They included a few Republicans and Clinton supporters.

Obama pressed members of Congress, who make up about a third of the 260 or so undeclared superdelegates, to declare their fealty publicly.

He added two, Representatives Brad Miller of North Carolina and Rick Larsen of Washington state, and also picked up the support of David Bonior, the former national campaign manager for John Edwards, who has stayed neutral. Bonior was the second-ranking Democrat in the US House for most of Bill Clinton's presidency and for 26 years represented Michigan, a key swing state in the fall. Bonior cited Obama's resounding win Tuesday in North Carolina, and said Obama can carry on Edwards's focus on poverty and working families.