PPP has polled on the impact of a Barack Obama endorsement in 5 key Senate races over the last month, and it's looking more and more clear that there's just about nowhere Democratic candidates would benefit from having the President come to campaign with them.
In Illinois, Louisiana, Pennsylvania, Ohio, and Wisconsin an Obama endorsement comes down as a net negative impact on the chances of a voter supporting a candidate by anywhere from 14 to 33 points. There are two reasons for that. First, Republicans respond more negatively to Obama than Democrats do positively. Second, independents are completely unimpressed by an Obama endorsement. In Ohio 6% say they're more likely to support an Obama endorsed candidate while 57% say they're less likely to. In Wisconsin it's a 6/51 spread. In Pennsylvania it's 10/56. In Illinois it's 15/39 and in Louisiana it's 16/49.
In less than two years Obama has brought about a massive change, from being a sought after endorsement and rising star to being the piranha of the Democratic party.
Hope and change baby.
Go take a look at the state by state Obama endorsement impact numbers over at PPP, linked above.