The Senate Conservatives Fund is throwing its support to Tea Party-backed candidate Rob Maness (R) in Louisiana, potentially complicating Republicans' hopes of defeating Sen. Mary LandrieuMary Loretta LandrieuLandrieu dynasty faces a pause in Louisiana Senate GOP rejects Trump’s call to go big on gun legislation Project Veritas at risk of losing fundraising license in New York, AG warns MORE (D-La.).

Mainstream Republicans have coalesced around Rep. Bill CassidyWilliam (Bill) Morgan CassidySenate GOP urges Trump administration to work closely with Congress on NAFTA GOP, Dem lawmakers come together for McCain documentary Graham working on new ObamaCare repeal bill MORE (R-La.) as their preferred nominee in the race. Maness's presence on the ballot and boost from the national conservative group could hurt Cassidy's campaign — and GOP hopes of retaking the Senate, as Louisiana is a top target.

The Senate Conservatives Fund's support will likely boost Maness's fundraising. They offer an implicit critique that Cassidy is a "Washington insider" in their endorsement.

"Colonel Rob Maness is a constitutional conservative with a remarkable record of service to our country," Senate Conservatives Fund President Matt Hoskins says. "He understands the value of our freedoms and will fight to repeal Obamacare and stop the massive spending, bailouts, and debt that are bankrupting our country. He offers voters a compelling choice over Senator Mary Landrieu because he's not a Washington insider. Colonel Maness is a principled leader who will make Louisiana proud."

The Senate Conservatives Fund was a vocal opponent of reopening the government during the shutdown unless Republicans could secure major concessions on ObamaCare, and has since backed a number of GOP challengers to sitting senators based partly on that vote. Cassidy voted against the bill — and with the group — on that bill, but it seems that one stand wasn't enough for them.

Maness quickly touted the group's support.


"This significant national endorsement is a sign of the continuing momentum started by the people here in Louisiana," Maness said in a statement. "I am very happy to accept this endorsement and I'm incredibly thankful to the Senate Conservatives Fund and to the diverse Louisianans who supported my campaign in its early days. They made this possible."

Louisiana's unusual primary system means any traction for Maness might not hurt Cassidy as much, however. Louisiana has an all-party primary on election day and if no candidate reaches 50 percent there's a runoff a month later.