I've been arguing that the dynamic of Michelle Bachmann's campaign is somewhat analogous to Barack Obama's in 2007. Obama trailed badly in the national polls throughout 2007. But he had high favorability seemed to do well among those voters most attuned to the campaign, which suggested that as elections neared and voters paid more attention, he had the potential to win over voters who were not paying attention months and months before any vote.
You can see a similar thing going on in Iowa. Another poll has Bachmann narrowly leading, but her lead expands when the sample is confined to voters paying a lot of attention:
One caveat, of course, is that a Rick Perry candidacy might hurt her. But Bachmann is positioned very well so far.