Giuliani and Romney both ran unsuccessfully for the Republican presidential nomination in 2008. Giuliani said Romney, who is mounting another bid for the White House, has changed his supposed views on everything from abortion to the individual healthcare mandate to cap-and-trade and gun control.
"I've never seen a guy change his positions on so many things, so fast, on a dime, on everything," Giuliani said on MSNBC's "Morning Joe."
"Pro-choice, pro-life. And pro-choice because somebody, a close friend, died, and he became pro-choice because this woman died of an abortion. Then he figures out there are embryos and he changes."
Giuliani compared former House Speaker Newt Gingrich to Ronald Reagan in the early days of the 1980 campaign. He said Democrats feared a George H.W. Bush candidacy and hoped Reagan would be the Republican nominee.
Giuliani described what he said was the conventional wisdom: "Ronald Reagan was the dumb actor, Ronald Reagan said incendiary things, Ronald Reagan was like Newt -- gosh, you never knew what he was going to say and the whole world would go crazy -- The New York Times would write editorials."