"This is like watching a Greek tragedy. It’s the negative campaigning and the increasingly personal attacks ... it should have stopped long ago. Any utility from the debates has been exhausted, and now it’s just exchanging cheap shots and personal shots followed by super PAC attacks."

McCain said he believes Romney will win his own home state as well as Arizona, but he disagreed with conventional wisdom that the sparring will toughen the eventual nominee as it seemed to when Obama fought off a tough challenge from Hillary Clinton in 2008.

“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, referring to Clinton’s famous attack ad against Obama. “Compare that to ‘Massachusetts liberal’ and “Romneycare’... These people are not respectful.”