McCain said the kind of attacks thrown between the GOP candidates are far worse than those lobbed between then-Sens. Barack ObamaBarack Hussein ObamaTrump's tariffs are a case of crony capitalism Obama to visit Kenya, South Africa for Obama Foundation in July Overnight Energy: EPA declines to write new rule for toxic spills | Senate blocks move to stop Obama water rule | EPA bought 'tactical' pants and polos MORE (Ill.) and Hillary ClintonHillary Diane Rodham ClintonColorado governor teases possible presidential run Mueller asks judge for September sentencing for Papadopoulos House Judiciary Committee subpoenas FBI agent who sent anti-Trump texts 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."