There was a general sense of Russ Feingold having dodged a bullet when ex-Gov. Tommy Thompson decided not to run (in PPP's March poll, Feingold led Tommy Thompson 47-44). In a bit of a surprise, though, likely GOP nominee Ron Johnson performs about as well as Thompson, trailing Feingold only 45-43. PPP's Tom Jensen speculates Republicans may have actually done themselves a favor here by running a fresh face (Johnson) instead of the stale Thompson; with only 20/18 favorables right now, Johnson does certainly have a lot of upside. (Feingold's approval is 42/42.) Of course, on the other hand, some of Johnson's support now may simply be because he's something new and different, and while Thompson had some moderate crossover appeal, the very conservative Johnson may not have much of that once the candidates start talking about specifics.
PPP may have run into a more conservative batch this time than last time; today's sample broke 48 Obama, 47 McCain, and it's also apparent in the trendlines for the low-profile Some Dude in the race, Dave Westlake. Regardless, it's a pretty clear signal that Russ Feingold (and the DSCC, unfortunately) are going to have to fight this one out.