Is David Vitter vulnerable to a primary challenge? Here are some thoughts on the issue:
-Vitter's approval numbers within his own party on our most recent poll were a good deal better than those of Arlen Specter and Blanche Lincoln at similar junctures before their closely contested primaries. 65% of Republicans in mid-June said they approved of the job Vitter was doing while 24% said they disapproved. That compares pretty favorably to where Specter was with Democrats in early April (53/30) and to where Lincoln was with them in February (51/35). The two of them ended up in what were more or less 50/50 races so based on that metric you would expect Vitter to get around 60% in a tough primary campaign.
-At the same time just because Republicans approve of Vitter doesn't necessarily mean the door is closed to their supporting someone against him in the primary. Last July we found that Vitter stood at a 62/19 approval spread within his party. But when we asked Republicans whether they thought Vitter deserved to be reelected only 56% said yes, while 29% said they thought it was time to give someone else a chance. Those figures would suggest a higher level of vulnerability for him.
It's hard to say at this point how strong of a challenger Chet Traylor will prove to be for Vitter but based on his standing in our polls over the last year I'd expect Vitter to get 55-65% in a Republican primary- a little weak for an incumbent but not horrible.
I think Democrats should be rooting for a 51-49 Vitter victory. Vitter's under performing in the polls right now for a Republican in Louisiana, given how unpopular Barack Obama is in the state. The small chance Democrats have at winning the race would probably evaporate to zero if the GOP's candidate didn't have Vitter's baggage. But Democrats need Vitter to be more bloodied up than he is already, and if Traylor can do that without actually winning Charlie Melancon might just have a chance this fall.