Adley's move comes a month before the state's new Republican governor, Bobby Jindal, takes office. Adley called himself a conservative reformer with the same philosophy as Jindal.

In discussing the party switch, the longtime Democrat Adley said he wants to be as effective as possible in dealing with the new governor.

"I have worked with a number of reform governors and spent years trying to get reform in Louisiana," Adley said during his announcement at the Bossier City Municipal Complex. "We've gotten close; we've never gotten there. I really believe this administration has that chance and I want to participate in that."

With Adley, Republicans now have 16 members in the Senate. Democrats have 23.

Adley is about to begin his second term in the Senate. He was a member of the state House of Representatives from 1979-95.

The Associated Press contributed to this report