Maybe half or more of all the US presidents (and a large percentage of all American married men) should have been or are automatically disqualified to serve as president. I see posts regularly that deride Kennedy and Clinton for their marital infidelities.
Is it wrong to bring that up?
No, not wrong to bring up at all. It is not a resume enhancer by any stretch. But to me at least, and I can only speak for myself, it is not necessarily a major reason to think someone can't be an effective president (or candidate). Particularly if they have recognized that what they did was wrong and repented. On that honest peoples' opinions can differ. But for anyone on the Left, with the history their favorites have, it is high hypocrisy to make an issue of it.
Finally, I think there are other and more serious reasons to have second thoughts about Mr. Gingrich and plenty of factors in his favor as well. None of these guys is perfect but any of them would be a marked improvement over what the country has now. Personally, except that I do NOT plan to vote for either Romney or Paul in the primary, I'm still undecided.