Devin Henry with the Minnesota Post tweets:
Michele Bachmann's office says she was withdrawn her dual Swiss citizenship.
Bachmann: "I took this action because I want to make it perfectly clear: I was born in America and I am a proud American citizen."
(Full statement avilable at Talking Points Memo.)
Politico originally reported that Bachmann became a Swiss citizen on March 19th.
So either you believe it took her 52 days to come to the conclusion that she was too proud of her American citizenship to stay a dual citizen, or something happened more recently to change her mind, such as this rather surprising information becoming public.
But we can't accept that second conclusion, because that would imply Bachmann doesn't make principled decisions.