[Talking Points Memo] A new Research 2000 poll suggests that Senator David Vitter (R-LA), the staunch social conservative who became bogged down in the D.C. Madam prostitution scandal in 2007, could potentially be vulnerable in 2010.

Vitter is still ahead in the primary and general elections, but in both cases he’s scoring below 50% — and that’s before having to go through an actual campaign, where his personal and policy issues could all get dredged up.

In the Republican primary, Vitter attracts 43% of the vote, Secretary of State Jay Dardenne (used here as a stand-in for some reasonably well-known Republican) gets 32%, and porn star Stormy Daniels is at 1%. Louisiana primaries have runoffs, by the way — so if multiple GOP challengers get in and Vitter were ahead but under 50%-plus-1, he would have to face a second round.