When Elephant Watcher began analyzing the 2012 Republican presidential primary, a similar post was needed to explain Donald Trump's low ranking. At the time, he was doing very well in the polls, too. Perhaps the best way to answer the Bachmann question is to thoroughly list the hurdles she must overcome before she can win the nomination.
1. Media Onslaught. Bachmann is despised by the media--on both the left and the right. For the moment, the media views her poll numbers as a symbol of the Republican field's weakness. But if she continues to post good numbers, they will consider her a more serious threat. Public curiosity about her well grow, and media scrutiny will intensify.
2. Name Recognition Advantage Fades. She may not be as famous as Mitt Romney or Sarah Palin, but Bachmann has a lot of name recognition. This accounts for a large portion of her polling. Consider: Other than Romney, the only candidates in the race with greater name recognition than Bachmann are Newt Gingrich (has a lot of baggage, suffered disastrous campaign setbacks, lacks a natural constituency) and Ron Paul (cannot win). Everyone else is essentially unknown. When early primary voters begin paying attention to the race, the name recognition advantage will fade, allowing candidates like Herman Cain and Tim Pawlenty to chew away at Bachmann's support.
3. New Candidates. If a candidate has both Tea Party support and is considered significantly more electable than Bachmann, that candidate will seriously threaten Bachmann. At the moment, the other Tea Party favorite is Cain, who is likewise considered unelectable. But if Rick Perry, Chris Christie, or both enter the race, Bachmann has a big problem on her hands.
4. Unforced Errors. It's a long time between now and the Iowa Caucus, which Bachmann must win. Every time Bachmann makes a gaffe, the media will endlessly replay it to build the narrative that Bachmann is unserious, weird, or cannot win. It's difficult enough for a disciplined candidate to avoid mistakes. Bachmann has a history of gaffes, and must avoid them from now on. Each error will be a high-profile one.
5. Frontrunner-itis. If Bachmann continues to do well, other candidates will begin to attack her. Bachmann is not the only candidate who needs a win in Iowa. The gloves will come off as the date of the Iowa Caucus approaches.
6. Electability Valued. As Iowa draws near, voters tend to coalesce around an electable candidate. The winners of the Iowa Caucus have been considered electable, and not always conservative. Even those who initially support a charismatic or exciting candidate often switch to a more sober choice at the last moment.
7. Strategic Voter Shock. If Bachmann does manage to win Iowa, it will create a panic among strategic voters (i.e. those who want an electable candidate, even if he's not the most conservative in the field). They will flock to whomever is leading in New Hampshire (most likely Romney), where he will have an anti-Bachmann firewall, even if they don't like him very much. Everyone who is afraid of giving away the 2012 general election will coalesce around the New Hampshire winner to defeat Bachmann. A grinding battle will ensue and last for the remainder of the primary season.
None of these difficulties are yet accounted for in the early polls. Thus, Bachmann's support is greatly exaggerated. Vaulting over the hurdles in front of Bachmann will be no easy feat.