I was quoted in Saturday's New York Times story criticizing Barack Obama's long association with someone he should shun: former Weather Underground bomber William Ayers. John McCain and Sarah Palin have good reason to fault Obama for overlooking Ayers' indefensible past. But while they're at it, they should also explain to the American people why McCain has been friends with another violent political extremist: Gordon Liddy.

Liddy, who worked for President Nixon's campaign, was convicted and sentenced to 20 years in prison for multiple crimes in burglarizing the Democratic National Committee office in the Watergate building--part of a broader plot to steal the 1972 election through sabotage, illegal spying and other dirty tricks. He even planned the murder of a journalist, though that idea was overruled. Bombings? He proposed the firebombing of a liberal think tank.

Liddy, now a conservative radio host, has never expressed regret for this attempt to subvert the Constitution. Nor has he developed any respect for the law. After the 1993 raid on the Branch Davidian compound in Waco, he endorsed the shooting of federal agents: "Kill the sons of bitches."

Yet none of this bothers McCain. Liddy has contributed thousands of dollars to his campaigns, held a fundraiser for McCain at his home and hosted the senator on his radio show, where McCain said, "I'm proud of you." Exactly which part of Liddy's record is McCain proud of?

While Obama has gotten lots of scrutiny for his connection to Ayers, McCain has never had to explain his association with Liddy. If he can't defend it, he should admit as much. And if he thinks he can defend it, let him.