BATON ROUGE, La. (AP) — In his bid to oust Louisiana'slongtime Democratic senator, Republican U.S. Rep. Bill Cassidy is battling perceptions in his own party that he may not be the best candidate.

Some conservatives question his credentials. Others wonder whether the soft-spoken man has the presence to stir up support to keep Sen. Mary Landrieu from a fourth term.

Landrieu has been called vulnerable in each of her elections to Congress, but she's managed to win even as Louisianavoters trend increasingly red in national races.

The GOP is looking for a rock-solid candidate who can fire up the Republican base while generating enthusiasm from moderates and independents.

Leaders of some Washington-based Republican organizations haven't thrown open their arms and endorsed Cassidy, privately saying they've heard rumblings that other GOP candidates could surface.