MESA, Arizona—After a disappointing debate performance in which Mitt Romney and Ron Paul successfully attacked him, Rick Santorum suggested that his two opponents are working together.

"You have to ask Congressman Paul and Governor Romney what they have going on together," Santorum said. When a reporter asked if he thought they were in cahoots, Santorum replied "You tell me?"

Romney adviser Stuart Stevens called the suggestion "whiny silliness."

"The notion that Ron Paul would do anything but speak his mind is not an argument he's going to be able to push that far," Stevens said. "If ever there was an iconoclast who got up there and said what he believes it's Ron Paul."