With ABC, CBS and NBC expected to provide only an hour of prime-time coverage each night of the convention, planners said the need to keep the program tight and on schedule was a more important consideration than the hurt feelings that might arise from excluding someone.

That means for now, Mrs. Bachmann, Mr. Perry, Mr. Cain and Mr. Gingrich are out. Rick Santorum, the only Republican to challenge Mr. Romney seriously in the delegate count, will speak. Representative Ron Paul will not. But his son Rand, a senator from Kentucky, will. That gesture could help appease Ron Paul agitators who might be looking to disrupt the proceedings, a threat that convention organizers are taking seriously.

But the fissures within the party will not be so easy to paper over, Mr. Gingrich said.

“The tension between the emerging party wings and the traditional party is going to be permanent and will mark the next eight years if Romney is president or if he’s not,” he said. “It’s just a fact.”