It does not appear that the picture was Photoshopped.
Instead, it is an actual photo of Bachmann which has succeeded in getting her additional publicity.
Even if not photoshopped, was it posed or was it taken from a pool shot on the campaign trail? If I follow them around with a high speed camera long enough, I’ll come up with whatever instantaneous facial expression I need to make someone look however I want them to.
Every photo that appears on a magazine cover is touched up. It will be cropped, the contrast adjusted, the focus sharpened or diffused depending on the look the editors want, etc. Photoshop or some other more purpose specific software was used on this one too. The question is whether or not the expression was intentionally altered to defame the candidate.