Feingold is generally considered (by people who aren't in love with him) to be a fairly weak candidate, right? He never won by large margins, imposed campaign finance restrictions on himself and took unpopular positions. That should reduce his popular vote margin. He'd probably run like Kerry + near uniform swing of a few points.
I wouldn't quite say that. He won by a decent margin in 2004, and he did have some more popular positions to focus on-ending Iraq ASAP, banning earmarks, etc.
For a bid for a third Senate term in a state carried by his party's Presidential nominee, it was nothing great. I'm not saying he'd lose or anything, just that he wouldn't be as strong a candidate as either Obama or Clinton were/would have been. Hence, he'd probably do about a point or so worse.
