Presumptive Republican nominee John McCain condemned Barack Obama's relationship with a controversial radical activist during an interview Sunday on ABC's "This Week."

Speaking of William Ayers, a college professor who was once part of the violent Weather Underground group and served on the same charity board as Obama, McCain said:

"His relationship with Mr. Ayers is open to question ... if you're going to associate and have as a friend and serve on a board and have a guy kick off your campaign that says he's unrepentant, that he wished (he) bombed more."

Obama's campaign was quick to respond to McCain's remarks on Sunday, saying the Arizona senator is "unable to sell his out-of-touch ideas on the economy and Iraq" and "has stooped to the same smear politics and low road that he denounced in 2000."

"The American people can't afford a third term of President Bush's failed policies and divisive tactics," Obama campaign spokesman Bill Burton said in a statement.

The Obama campaign also drew attention to a statement made by McCain's senior adviser Charlie Black, who said the Arizona Senator believes "candidates cannot be held accountable for all the views of people who endorse them or people who befriend them" during a March 14 interview on MSNBC.

McCain also has taken criticism for seeking the endorsement of the Rev. John Hagee, an evangelical Christian pastor who has been criticized heavily for anti-Catholic remarks. McCain on Sunday told ABC that it was "probably" a mistake to seek Hagee's endorsement.

But, he added, "I admire and respect Dr. Hagee's leadership of the, of his church. I admire and appreciate his advocacy for the state of Israel, the independence of the state of Israel."

McCain also said he condemned "remarks that are made that has anything to do which is condemning of the Catholic church."

McCain also criticized Obama for comparing Ayers to Sen. Tom Coburn, R-Okla., during Wednesday's ABC News democratic presidential debate.  Obama said he did not agree with the views held by many of his associates, including Coburn, who once proposed the death penalty for those who perform abortions.

"Worst thing of all, that, I think, really indicates Senator Obama's attitude, is he had the incredible statement that he compared Mr. Ayers, an unrepentant terrorist, with Senator Tom Coburn, Senator Coburn, a physician who goes to Oklahoma on the weekends and brings babies into life," McCain said.

"Comparing those two -- I mean, that's not -- that's an attitude, frankly, that certainly isn't in keeping with the overall attitude," he said.

Hillary Clinton was first to raise questions over Obama's relationship with Ayers during Wednesday's debate.

In his defense, Obama has said that Ayers is "a guy who lives in my neighborhood" and not someone who has endorsed him or talked to him often.

"The notion that somehow as a consequence of me knowing somebody who engaged in detestable acts 40 years ago when I was 8 years old, somehow reflects on me and my values, doesn't make much sense," Obama said at this week's debate.