An awful lot of progressives who admire Wellstone sometimes forget that even he was still in the process of evolving. In 1996 he voted for DOMA. I remember being extremely disappointed in him at the time.
In the end, I think he was perhaps disappointed in himself as well. Here's what he said about that vote later in his book The Conscience of a Liberal:
What troubles me is that I may not have cast the right vote on DOMA. I might have rationalized my vote by making myself believe that my honest position was opposition [to same sex marriage]. This vote was an obvious trap for a senator like me, who was up for reelection. Did I convince myself that I could gleefully deny Republicans this opportunity? . . . When Sheila and I attended a Minnesota memorial service for Mathew Shepard, I thought to myself, 'Have I taken a position that contributed to a climate of hatred?' . . . I still wonder if I did the right thing.It is that kind of courageous self-examination that allows for evolution.