Another Prominent Republican Supports Obama

Buckley, who praised McCain in a New York Times Op-Ed earlier this year and defended the Arizona senator's conservative credentials against wary talk-radio hosts, said McCain is no longer the "real" and "unconventional" man he once admired.

"This campaign has changed John McCain," Buckley wrote. "It has made him inauthentic. A once-first class temperament has become irascible and snarly; his positions change, and lack coherence; he makes unrealistic promises, such as balancing the federal budget 'by the end of my first term.' Who, really, believes that?

"Then there was the self-dramatizing and feckless suspension of his campaign over the financial crisis," Buckley added. "His ninth-inning attack ads are mean-spirited and pointless. And finally, not to belabor it, there was the Palin nomination. What on earth can he have been thinking?"

But Buckley made clear he's not just voting against McCain, praising Obama for his "first-class temperament and first-class intellect.

"Obama has in him—I think, despite his sometimes airy-fairy 'We are the people we have been waiting for' silly rhetoric—the potential to be a good, perhaps even great leader. He is, it seems clear enough, what the historical moment seems to be calling for," Buckley wrote.