Well, this is interesting.

It wasn't the ignorance of "Ubeki-beki-beki-stan-stan" that torpedoed Herman Cain's surprisingly popular run for the Republican presidential nomination. It wasn't his confusion on Libya, the revelation that his 9-9-9 plan would nearly double the taxes on many Americans, his back and forth on abortion or even two settled sexual harassment claims.

Instead it was a mistress claiming a 13-year consensual affair — complete with text records and a flirtatiously signed book — and probably some pleas from his wife Gloria to stop embarrassing her. Cain has denied all the allegations of inappropriate or extramarital sexual conduct but says the rumors have hurt both his family and his ability to raise funds.

"That spin hurts. It hurts my wife. It hurts my family. It hurts me and it hurts the American people," said Cain from his campaign's Atlanta headquarters. "I'm suspending my campaign not because we are not fighters, not because I'm not a fighter, it's just as we went through this re-assessment of the impact on my family, the impact on you, my supporters .... as well as the impact on the ability to raise the necessary funds to be competitive, we had to come to this conclusion."

Polls in October had given Cain as high as 23 percent of the Republican vote in Iowa, but his popularity waned in recent weeks, with only eight percent of likely caucus-goers in that state preferring Cain in the most recent Iowa Register poll.

The question for the Republican race is who's going to inherit Cain's supporters? A surging Newt Gingrich is the most likely candidate, although it seems more than a little ridiculous that votes for one man brought down by an affair would go to another man who 1) had an affair and demanded a divorce while his first wife was in the hospital with cancer and 2) had another affair while attempting to impeach the president for the same behavior.

But if Iowa voters are consistent in their demands of marital fidelity, the beneficiary could be Rick Perry, who has proven a gaffe machine but still has a stockpile of soft money. Michelle Bachmann's star has dimmed with her poll numbers, but she's got a Midwest connection and flawless evangelical credentials.

One candidate who won't be happy to see Cain go is Mitt Romney. Without Cain in the pack to help split the cultural conservative and Tea Party votes, his frontrunner position in Iowa could be at risk.