Continued from page 1

Some Republicans argue the primaries have strengthened Mr. Romney’s candidacy in the same way a rugged primary challenge from Hillary Rodham Clinton helped Mr. Obama in 2008, but G. Terry Madonna of the Franklin and Marshall Center for Politics said there’s a big difference.

“I think there is a growing realization … that this battle has to end. That with each passing week it has gotten personal, it’s gotten divisive,” Mr. Madonna said.