On the other hand, I (admittedly) don't remember the Trent Lott flap very well, either.

There are two standards that I would hold a person to in this case:

a) Could they be reasonably expected to know about this person's past behavior

and

b) If not, then once made aware of the past activities of such a person, how they respond to the knowledge.

Doesn't matter to me if they are Democrat or Republican.