GOP Rep. John Fleming announced  Thursday he would not join the Louisiana Senate race, saying his entrance into the contest could thwart a GOP pickup of the Democratic-held seat.

Fleming said he decided to opt out of the race after fellow Louisiana Rep. Bill Cassidy announced Wednesday that he would be challenging vulnerable Democratic Sen. Mary L. Landrieu.

“For me to enter the race now would risk a contest between two experienced Republican Congressmen, potentially offering Senator Landrieu a path back to Washington,” Fleming said in a statement. “I can’t let that happen.”

Fleming’s announcement is a shift from his tune earlier in the week, when he said “I haven’t ruled anything out.”

With Fleming out, political observers are now awaiting word from former Rep. Rep. Jeff Landry, who is still deciding whether to run. In an interview with CQ Roll Call earlier this week, Landry said he will have an announcement next week that “may have the ability to play in this race” but declined to elaborate further.

Fleming is the third prominent Louisiana Republican to decline a run in what is expected to be one of the most competitive Senate races this cycle. Rep. Charles Boustany Jr. and Lt. Gov. Jay Dardenne, who had been mulling over runs, have already announced they won’t run for the seat.

Louisiana Republican Sen. David Vitter praised Fleming’s decision.

“John is a real fighter, and I think his stature and role in the House will grow enormously,” Vitter said in a statement. “His announcement also makes it clear that Bill Cassidy will be the single major conservative challenging Mary Landrieu. It should be a very competitive race, and one that will help decide whether Harry Reid and Barack Obama continue to run the U.S. Senate.”