I usually don’t write about single-state 2012 polls, but hoo boy. He was at 52 percent in March, more than 30 points ahead of Huckabee, and now? 21 percent, two points behind Huck. What happened? PPP’s theory:

Why has Romney fallen so far? I think part of the reason he polled so well earlier in the year is that he was the anti-Palin. Palin’s favorability numbers with GOP voters in Florida are a good deal worse than they are most places and Romney did well in those earlier surveys as one of the few named alternatives to her. As more response options were provided in later polls the anti-Palin sentiment was diffused across several candidates and Romney’s mile wide but inch deep support declined further and further and further to where it is now.

Romney’s chances at the Republican nomination really might be contingent on a small pool of candidates running- the more ‘reasonable’ folks there are in the mix the worse Romney does because he doesn’t have a real solid base of support. If there are 5 ‘competent’ folks who have been Governors or Senators running it may be hard for any of them to break out as a strong alternative to Palin should she make the race.

An important caveat: The March poll was based on a hypothetical three-way race. In July they re-polled it with Gingrich in the mix and Mitt’s numbers collapsed from 52 percent to 31, with Newt picking up 23 percent. Disastrous, right? Maybe not: The takeaway from these numbers, I think, is that Florida’s ripe for the picking by whichever centrist candidate is left standing after the Iowa/New Hampshire/Nevada/South Carolina gauntlet. Huckabee and Palin, the two most prominent social cons in the race, have been stuck below 40 percent combined since PPP started polling the state earlier this year. If Romney manages to win New Hampshire and Nevada, say, that should clear out the rest of the centrist/managerial candidates like Gingrich by the time Florida rolls around and leave him as the only alternative to whichever social conservative emerges from Iowa and South Carolina. This is Romney’s great weakness but potentially also his great strength — as Frum noted last month, his support derives chiefly from him being a bland but acceptable alternative to more vibrant candidates whom many primary voters dislike. (E.g., Romney would, I expect, handily win a Hot Air primary head to head against Huckabee on the Anyone But Huck platform.) By the time he gets to Florida, the die will already have been cast. If he wins the Generic Competent Electable Guy mini-primary early on between him, Newt, Pawlenty, Daniels, and Thune, he’s well positioned to win Florida notwithstanding his polling right now. Which, of course, explains why Palin supporters are hoping for a centrist stalking horse to emerge and peel votes away from Romney.

Exit question: What happens if neither Palin nor Huckabee nor Pence runs? Bill Kristol and Peggy Noonan both speculated yesterday that she’ll sit this one out; Pence is reportedly more interested in running for governor, and rumors have been swirling for a week that Huck is keen on sticking with TV. Would Gingrich become the social con choice in that case? Given how much support he bleeds from Romney as a “managerial” alternative, he’d be mighty formidable with the base behind him too.