Ed Kilgore has an excellent piece over at TNR about the challenges Michele Bachmann faces as she tries to move from gadfly to actual presidential contender. As he points out, she's going to be pressured, both by the press and by rival candidates. Click through and read the whole thing for his analysis, which I think is quite good.
To add to it, however, I'd say that Bachmann's sweet spot is, it seems to me, exceedingly small. If she gives conventional answers to tough questions, she runs the risk of being Just Another Conservative, albeit one with a back-history of oddball statements and positions. In other words, by doing what she can to reassure the people in the party who care about winning in November, she risks her ability to stand out from the Cain-Santorum part of the field.
Another way to look at it: there just isn't much actual policy space to the right of Romney, Pawlenty, and (presumably) Perry for Bachmann to occupy by herself, even if she could monopolize that space -- at least, not much space that won't get her labeled a nut. That leaves attitude, not policy positions, but the sorts of things that signal that she's a true believer are problematic for plenty of people.
And yet if she doesn't do that...well, we're a long ways from Iowa, still. Six months of campaigning as a regular mainstream conservative, and it wouldn't be surprising if a lot of rank-and-file voters see her as one, and look to Cain or one of the others (Roy Moore!) for a real insurgent candidacy.
Which gets back to Kilgore's point: she's going to be tested, and she's going to have to be an awfully good politician to get through it and wind up as viable as many (but, still, not me) currently believe she is.