In a move almost certain to presage a challenge to Sen. Mary Landrieu (D-La.) next year, Louisiana state Treasurer John Kennedy announced Monday that he is switching political parties and becoming a Republican.

“For the past several years, it has increasingly been the case that those public servants who have embraced my ideas and my philosophy of trying new approaches are primarily Republicans,” Kennedy wrote in an e-mail to supporters.

Kennedy made no mention of the 2008 Senate race in his statement, saying only that he planned to seek a third term as treasurer as a Republican this November. But Kennedy ran unsuccessfully for the Senate as a Democrat in 2004, and he has been wooed by White House political strategist Karl Rove and other leading Republicans to make the switch and take on Landrieu, who currently is seen as the most vulnerable Democratic Senator up for re-election.

“Mr. Kennedy’s commitment to the Republican Party is a step in the right direction for all of our citizens who strive for a better Louisiana,” state Republican Party Chairman Roger Villere Jr. said in a statement. “He realizes that the time for change in our state is now, and he will be an essential part of the team which will work to transform Louisiana next year.”

Prior to serving as state treasurer, Kennedy was a cabinet secretary and top aide to another party switcher, former Gov. Buddy Roemer, who was elected as a Democrat and later became a Republican.

Because there is an open gubernatorial race in Louisiana this fall and several other statewide positions also are on the ballot, the 2008 race in the Pelican State has been slow to develop. Many political observers believe the outcome of the fall elections could have a bearing on the political dynamic in the state — Landrieu’s fate — next year.