Clinton May Be Hopeful, but Obama Rolls On

Still, despite a series of trials that have put Mr. Obama on the defensive and illustrated the burdens he might carry in a fall campaign, the Obama campaign is rolling along, leaving Mrs. Clinton with dwindling options.

Mr. Obama continues to pick up the support of superdelegates — elected Democrats and party leaders — at a quicker pace than Mrs. Clinton.

On Thursday, he got a boost from a high-profile defection: Joe Andrew, a former Democratic national chairman appointed by former President Bill Clinton, said he had changed his mind and would back Mr. Obama. Even after Mrs. Clinton’s victory in Pennsylvania, Mr. Obama has held on to a solid lead in pledged delegates, those selected by the voting in primaries and caucuses.