There's still a lot of campaigning to do. Didn't polls have Cain leading just a month ago?
In Michigan? None that I recall.
Nationwide he was. My point is, like it has been said time and time again, the only "poll" that matters is the primary/caucus results. The race has been so fluid that I wouldn't take a poll to seriously until about a week or two before that state votes. Remember back in August when Perry had a commanding lead in South Carolina? He's down in the low, single-digits right now.
Though Gingrich probably won't have quite as drastic as a drop, there's still a good chance he'll at least drop low enough that Romney will have a shot - Romney has a huge cash/organization/endorsement advantage. This race is
far from over.