In the ad, a fellow prisoner of war, Philip Butler, says he would not like to see McCain in the White House because of the POW experience and the Arizona senator's temperament, The Hill, a Washington political publication, says.

The ad was produced by Brave New PAC, a political action committee associated with Brave New Films, which reportedly has no ties with the Democratic party.

"I think it is scandalous and disrespectful to a man who has obviously sacrificed greatly for his country," former Pennsylvania Republican Sen. Rick Santorum said.

He called the ad Obama's "nightmare that some crazy group suggests that because someone served his country and sacrificed for his country, that he is not capable to lead."

Butler served alongside McCain at the U.S. Naval Academy and later was imprisoned with him in Vietnam.