The GOP's single best pickup opportunity in the Senate right now is against Louisiana Dem Mary Landrieu -- but a new poll finds that she holds a solid lead over her Republican challenger, suggesting that this year's Senate map could be very rough indeed for the GOP.

The numbers from Rasmussen: Landrieu 55%, state Treasurer and ex-Dem John Kennedy (R) 39%. If Landrieu prevails this November, then the GOP is likely to be shut out on Senate pickups again, just as they were in 2006.