The only reason he squeezed in was lucky timing of Rod Grams worthless son being caught diddling a 15 year old girl in some seedy hotel just before the 2000 election.
Even Minnesota liberals like their candidates to be intelligent. I wouldn't surprised to see them to ask Dayton to step aside. If he refuses, however, I don't think they can force him out given his ample family fortune.
I thought Ron Wyden (OR) had that distinction.