The Obama campaign could have some internal polling numbers that say the Cain Train will split the black vote and end up being a landslide if he gets the nomination. If the numbers are bad enough, they may have played this card earlier than they wanted to get Romney or Perry back in the lead.
Romney would be my suspect. He's got the money. He's got the liberal tendencies. And he's not above dirty tricks. Perry and Bachmann would also be suspects, as they also have much to gain if Cain falters.
Romney is my top suspect too. Perry is next to try to set himself up as the main anti-Romney candidate which he was for his few weeks of fame. I could also see Ron Paul supporters behind it because they have that special combination of fanatic and crazy that you don't see very often.
LOL. That's an excellent point, amusingly put. RP slipped my mind altogether, but I could see that. Certainly some flamethrowers in his camp, not above this sort of thing.