Democrats have a big opportunity to expand their House majority today, and in a very unlikely place. The special election in Louisiana's Sixth District -- which gave 59% of its vote to President Bush in 2004 -- is being held today with Democrat Don Cazayoux favored to beat controversial Republican Woody Jenkins.

The GOP undertook an effort in the home stretch to tie Cazayoux, a social conservative, to the national party in general and Barack Obama in particular as an early experiment in using the Democratic frontrunner as a cudgel against down-ticket Democrats.

However, a Republican source tells TPM Election Central that while the ad has actually had some success, there isn't much optimism that it will be enough to pull Jenkins through: "Cazayoux's negatives have certainly gone up, but the question is whether or not it's been enough to make Woody Jenkins a viable alternative."

Polls close at 9 p.m. ET tonight.