A statement by Gerald Ford in a 1976 presidential debate is among the most memorable, however. Ford famously baffled audiences when he said, "There is no Soviet domination of Eastern Europe." Later pressed by the moderator, he refused to back down. The moment haunted the rest of his losing campaign.

Publicly, Perry aides sought to downplay Wednesday night's shaky answer.

"We had a stumble of style and not substance," insisted Ray Sullivan, Perry's top communications adviser. "He still named two more agencies than this president" would eliminate.

Perry had no public schedule on Thursday and planned to raise money privately at events in Tennessee. His next public campaign stops were scheduled in South Carolina on Friday -- a day before yet another debate.