Obama wins 2 more superdelegates; Clinton keeps campaigning

Meanwhile, Clinton continued to press her case that she was the candidate most equipped to defeat McCain in November, though new comments about race dogged her following an interview with USA Today published Thursday.

In it, Clinton cited an Associated Press article which found that "Senator Obama's support among working, hardworking Americans, white Americans, is weakening again, and how whites in both states who had not completed college were supporting me."

"There's a pattern emerging here," she said.

Obama's campaign did not respond to the comments, which generated buzz in the liberal blogosphere.

Clinton has repeatedly vowed not to drop out before June. But as the race drags on, fears mount that it could affect party unity, costing Democrats their best chance to reclaim the White House after almost eight years of Republican leadership.