ADELMAN…. There have been more than a few “Obamacans” this year — the group of relatively high-profile Republicans and conservatives who, for a variety of reasons, are supporting Barack Obama. We’ve seen some from current and former lawmakers (Leach, Gilchrest, Chafee), some Republican officials (Powell, Kmiec), and some well known political observers (Buckley), and even some conservative scholars.

But it never would have occurred to me that Ken Adelman would throw his support to Obama.

Ken Adelman is a lifelong conservative Republican. Campaigned for Goldwater, was hired by Rumsfeld at the Office of Economic Opportunity under Nixon, was assistant to Defense Secretary Rumsfeld under Ford, served as Reagan’s director of arms control, and joined the Defense Policy Board for Rumsfeld’s second go-round at the Pentagon, in 2001. Adelman’s friendship with Rumsfeld, Cheney, and their wives goes back to the sixties, and he introduced Cheney to Paul Wolfowitz at a Washington brunch the day Reagan was sworn in.

In recent years, Adelman and his friends Cheney, Rumsfeld, and Wolfowitz fell out over his criticisms of the botching of the Iraq War. Still, he remains a bona-fide hawk (“not really a neo-con but a con-con”) who has never supported a Democrat for President in his life. Two weeks from now that’s going to change: Ken Adelman intends to vote for Barack Obama. He can hardly believe it himself.

Adelman told George Packer that he’s basing his decision largely on questions of “temperament” and “judgment.” As Adelman sees it, McCain faced a temperament test when the financial crisis began, and McCain failed under pressure, becoming “impetuous, inconsistent, and imprudent; ending up just plain weird.”

McCain’s judgment test came when choosing a running mate, Adelman argued, and he failed that one, too.

Subsequently, Adelman added, “[McCain’s] hiring of the Bush attack squad, South Carolina 2000, made me view this honorable man as heading a dishonorable effort. And that’s still the case. It’s pretty disgusting, what he’s doing.”

Given Adelman’s background and ideology, I hardly know what to do with this information. Indeed, if Obama is elected, I can only assume Adelman will slam Obama’s foreign policy with some enthusiasm for his failures to start a series of new wars. With that in mind, it’s not as if Adelman is about to be welcomed into the Democratic fold with open arms.

But Adelman’s rejection of McCain, his erratic behavior, and his reckless judgment reflects just how far McCain has fallen. I don’t imagine Adelman carries the same kind of electoral significance as, say, Colin Powell, but if McCain can’t hold onto Adelman, it speaks to a broader and more significant problem for the Republican ticket.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.