The worst thing about Bachmann is that she won an election. People like her should be filtered by the electorate.
That said, having Bachmann run for president in 2012 pretty much tanked Romneys campaign. The poor guy had to go way further right than he wanted to on social issues to not lose to her in the primary's.
In fact, at one point, she actually lead the primaries. In 2012 Michelle Bachmann was almost the republican nominee for POTUS. That is terrifying.