McCain said the kind of attacks thrown between the GOP candidates are far worse than those lobbed between then-Sens. Barack ObamaBarack Hussein ObamaOvernight Energy: Dems ask Pruitt to justify first-class travel | Obama EPA chief says reg rollback won't stand | Ex-adviser expects Trump to eventually rejoin Paris accord Overnight Regulation: Trump to take steps to ban bump stocks | Trump eases rules on insurance sold outside of ObamaCare | FCC to officially rescind net neutrality Thursday | Obama EPA chief: Reg rollback won't stand Ex-US ambassador: Mueller is the one who is tough on Russia MORE (Ill.) and Hillary ClintonHillary Diane Rodham ClintonWoman behind pro-Trump Facebook page denies being influenced by Russians Trump: CNN, MSNBC 'got scammed' into covering Russian-organized rally Pennsylvania Democrats set to win big with new district map MORE (N.Y.) in the 2008 Democratic primary. 

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."