The Family Research Council's big "Values Voter Summit" in DC this weekend included a straw poll, which Romney won in a squeaker over Mike Huckabee. Huckabee was the clear favorite of those actually in attendance -- beating Romney 488 to 99 in the ballots cast on-site, according to a Chicago Tribune report -- while Romney made up the difference among FRC members who voted online. (Romney has been accused of trying to steal the straw poll by urging his supporters to sign up online as FRC members, in order to vote.)
Huckabee may be emerging as a serious problem for Romney, now that the actual field of GOP nominees has solidified. With Gingrich not running, Fred Thompson finally available for scrutiny (he doesn't attend church!), Brownback out, and others (Tancredo, Hunter, Keyes) clearly not viable, Huckabee has a real chance to convince "Christian conservative" voters to support him -- to convince them that he's not a wasted vote.
Huckabee has concentrated heavily on Iowa, where he also was the top non-Romney in the August Ames Straw Poll. A recent poll of likely Republican caucus-goers in that state put Huckabee in the high teens, which is enough for people there to start taking him seriously -- and not too far behind Romney, the leader at 28% in that poll.
It wouldn't take much for Huckabee to move into second place in Iowa polls, which would get people talking about whether he can win the state, which would get many tepid Iowa Romney supporters -- social conservatives who now support Romney as the least-bad of the frontrunners -- to flip to the rising Huckabee.
Until now, Romney has treated Huckabee -- wisely, I think -- as a small insect not worthy of his attention. For a frontrunner like Romney to engage with a second-tier candidate like Huckabee is to elevate the other guy. But Romney cannot afford to fall out of first place in Iowa, not for a second -- his first-place standing there is pretty much the only thing that justifies him being considered a top-tier candidate.
If Huckabee gets any additional bump in Iowa, I'd expect Romney to start attacking him.