The Democratic but pretty reliable firm Public Policy Polling shows Herman Cain surging to first place:
Cain is up 30-22 on Romney with Newt Gingrich sneaking past Rick Perry for 3rd place at 15% to Perry's 14% with Michele Bachmann and Ron Paul tied for 5th at 5%, Jon Huntsman 7th at 2%, Rick Santorum 8th at 1%, and Gary Johnson 9th with less than 1%. [...]
There are indications within the poll that Cain's stay at the top could be short lived. Only 30% of his supporters are solidly committed to him with 70% saying they might still go on to support someone else. Those numbers aren't much better for Romney, who only has 31% of his supporters solidly committed, or Gingrich, who only has 34% solidly committed. The strongest base of support among the Republican front runners- even if it's shrinking- is Perry's- 48% of his remaining backers say they'll definitely vote for him. Overall 70% of Republicans are either undecided right now or open to voting for someone different than who they're with now- that signals an extremely wide open race.
If Cain were to implode--like Bachmann and Perry before him--where would his supporters go? It seems they're more likely to go back to Perry or break for someone like Gingrich rather than support Romney:
If the race came down to a two way match between Cain and Romney, Cain leads 48-36. Cain would pick up Bachmann, Gingrich, Perry, and Santorum's supporters. Romney would get Huntsman and Paul's. Cain would absolutely crush Perry in a head to head, 55-27. He would win over the supporters of every other candidate, including Romney's by a 56-24 margin.
And that's why Romney, whose poll numbers have been stuck in the 20s for months, is not the inevitable GOP presidential nominee.