McCain recalled a widely discussed ad by the Clinton campaign questioning whether Obama would be ready to respond to a "3 a.m." emergency if he were elected president.
"That was nothing compared to this. The worst you got then was, ‘What are you going to do if you get that phone call at 3 in morning?’ " McCain said. "Compare that to ‘Massachusetts liberal’ and “RomneyCare’... These people are not respectful."
McCain's comments came a day before Michigan's primary. Both Mitt Romney and Rick Santorum have been campaigning hard in the state over the last few days.
The Santorum campaign began using a robocall urging Michigan Democrats to vote for the former Pennsylvania senator in the Michigan primary. In response, Romney said that Santorum had been using "dirty tricks" because his campaign is "desperate."