Barack Obama, Bill Clinton, and Sarah Palin will probably be the three biggest names out on the campaign trail this fall but whether any of them will be particularly effective for their chosen candidates looks debatable.
Voters in our newest national survey say that an endorsement from each of them is a net negative and it's not very close, ranging from 12 to 21 points. Palin is the most toxic with 51% saying her endorsement would turn them against a candidate and only 30% saying it would make them more likely to support someone. But President Obama is not far behind with with 49% saying his support would be a negative to 32% who say it would make them more inclined to vote for someone. Former President Clinton comes out the best- 31% say his support would increase their likelihood of voting for someone, similar to Obama and Palin's numbers, but only 43% say he would have a negative impact on their votes.
All three of them are somewhat effective with their party base, but even more of a turn off to voters in the opposite party. And independents aren't interested in hearing from any of them.
For Palin 57% of Republicans are more likely to vote for someone she endorses, but 81% of Democrats are more likely to vote against them, and independents respond negatively by a 53/24 margin.
For Obama 59% of Democrats are more likely to vote for someone he endorses, but 82% of Republicans are more likely to vote against them, and independents respond negatively by a 48/25 margin.
For Clinton 57% of Democrats are more likely to vote for someone he endorses, but 72% of Republicans are more likely to vote against them, and independents respond negatively by a 45/22 margin.
I don't think these kinds of poll numbers will keep any of these folks off the trail this fall but how useful their support is outside of primaries looks pretty debatable.
Full results here