But he projected Mrs. Clinton would receive a net gain of about 12 pledged delegates from her victory, leaving Mr. Obama with a lead of 159 pledged delegates, according to the campaign’s calculation.

“We don’t believe that the structure of the race is going to change,” Mr. Plouffe said.

In a conference call with reporters today, Mr. Plouffe sought to dismiss concerns about how Mr. Obama would fare against Mr. McCain. He ticked through a list of states where polls indicated Mr. Obama was a stronger opponent than Mrs. Clinton in facing Republicans.

“We think this is a flawed exercise to somehow suggest that performance in primaries is a leading indicator or what would happen in a general election,” Mr. Plouffe said. He added that Mr. Obama had a high favorability rating among Democrats who supported Mrs. Clinton.

The focus of the race on Wednesday immediately turned to Indiana and North Carolina, where 187 delegates at stake in the May 6 primary. Mr. Obama was scheduled to hold a town meeting Wednesday afternoon in New Albany, Ind., before returning to Washington to cast votes in the Senate.