During an appearance on CBS' "Face the Nation," Kerry said he has seen the Arizona senator change his personality and politics during his race for his party's nomination and in preparation for the upcoming general election.

"John McCain has changed in profound and fundamental ways that I find personally really surprising, and frankly upsetting," Kerry said.

"This is a different John McCain. This is not the Sen. John McCain; this is want-to-be president John McCain."

U.S. Sen. Lindsey Graham, R-S.C., appearing on the same program, attacked presumptive Democratic presidential nominee, Illinois Sen. Barack Obama.

Graham, an outspoken McCain supporter, said Obama is wrong to suggest the United States withdraw from Iraq.

"The big test for this country is, how do you avoid losing in Iraq? If we'd have listened to Barack Obama, we would have lost," he said. "If we listen to him now, we will lose in the future and undercut all the gains we've made."