Politico reports that at “a crowded Big Sky Diner in Ypsilanti, Mich., Herman Cain took umbrage about being pushed on the ‘Princess Nancy’ line about former House Speaker Nancy Pelosi.”Gone is the pleasant demeanor that characterized his campaign until now:

“You know, I remember when Speaker Pelosi called me and the tea party people AstroTurf,” he said. “I don’t remember anybody asking about that story.”

So then, why apologize?

“So you all would stop asking me about it. Ok? Look, I’m about the big issues, fixing this economy. I’m not focusing on stuff like that. So ask her why she called the tea party people AstroTurf a couple of years ago. That ought to be the question.”

Well, that settles that. Actually, not. It’s an annoying and childish attempt to shift responsibility away from his own behavior. He is the one running for president, not Pelosi (thank goodness).

It’s the same habit that got him into trouble during his defense against sexual harassment allegations. It’s racism. It’s the liberal media. It’s Texas Gov. Rick Perry. A string of accusations at some point suggests he’s either a downtrodden victim, ever the misidentified perpetrator, or a conspiracy-monger.

It also stands in contrast to his self-image as an executive who is responsible for the bottom line. Unlike government officials, he’s been telling us, he doesn’t pass the buck. You see in the private sector, you can’t blame someone else for your mistakes. Except he does it. All the time.

Cain has systematically undermined his public persona. He was optimistic; now he’s grouchy (for good reason). He was bold in presenting his 9-9-9 plan; Now he’s a crank who knows nothing other than 9-9-9. He was without talking points; Now that’s all he has.

The allure of having a businessman from outside the Beltway is that we would get an antidote to what ails D.C. But when the outsider weirdly comes to embody the characteristic we abhor, then why not get a regular pol who at least knows something about the issues?