At the start of the GOP debate last night, Herman Cain said, “I am businessman Herman Cain. I’ve been married to my wife, Gloria, for 43 years. And I’m a 42-year businessman, which means I solve problems for a living.” Here’s a problem: A candidate with no public experience bases his entire presidential campaign on a gimmicky tax plan that proves to be ill-conceived and objectionable to his natural base of supporters. He then goes on national TV, advocates exchanging all the Gitmo detainees for a hypothetical captured American, denies in a debate that he said it and then afterward admits he “misspoke.” How does this candidate come back?

You see the issue. The central issue last night was whether Cain could evolve from a congenial candidate to a serious presidential contender. The answer at the end of last night: Doesn’t look like it.

This about-face is cringe-worthy:

Brutal. It’s the sort of bubble-bursting episode that is not easy to live down.

On Nov. 15, he and his competitors will have to navigate through an entire foreign policy debate. That’s challenging for figures who have been in office for a long time. It’s easy to have a lapse on a name or get a sequence of events wrong. Without a working knowledge of some critical details, it is hard to fake competency on matters of war and peace. For those with zero interest in and prior knowledge of national security, it simply won’t be possible to fake it through an entire debate.

But Cain’s Gitmo moment and his opponents’ assault on his 9-9-9 plan simply confirmed what many suspected. Can someone who has never held public office really win the presidency? The suspended disbelief that such a thing could happen vanished last night. And with it, most of Cain’s traction. He remains popular among Tea Partyers, but the sense surely must be at this point that a vote for him is a vote thrown away.