Ignoring the “flake” question, for which Wallace later appropriately apologized, I thought that Bachmann did just fine on the discussion of gay marriage, states rights and the Constitution. Wallace seemed to think that she was being inconsistent, but I didn’t see that at all. Andrew McCarthy agrees.
Note that you don’t have to agree with Bachmann as to whether or not gay marriage is good or bad to agree that her position is the correct (and a consistent) one from the standpoint of process and law (just as one doesn’t have to oppose abortion to think Roe v. Wade a constitutional abomination).