Family Research Council President Tony Perkins is endorsing Rep. Bill Cassidy (R-La.) in his runoff against Sen. Mary LandrieuMary LandrieuMeet Mitch Landrieu, the 2020 dark-horse Dem Medicaid rollback looms for GOP senators in 2020 Five unanswered questions after Trump's upset victory MORE, reversing course to show unity within the GOP.

Perkins initially endorsed Tea Party-backed Col. Rob Maness in part because of concerns with Cassidy’s conservative values. Cassidy, along with a handful of Republicans, joined Democrats in 2009 to pass a law that made assaulting a person based on their sexual orientation a crime.

But Perkins changed his mind Thursday based on a conversation with Cassidy and after hearing him bash laws that could “use legal intimidation to attempt to limit freedom of faith and freedom of speech.”

“Because I believe you to be a man of principle and a man of your word, I am encouraged by these latest developments,” he wrote in a letter to Cassidy provided to The Hill. 

“It is critical to the pro-family movement in America that any conservative elected to the U.S. Senate clearly understands and acknowledges the severity of the threats posed to religious liberty—our first freedom—and pledges to defend it.”

On Election Night, Perkins told The Hill that he didn’t see himself supporting Cassidy without serious “assurances,” which he received in the subsequent days. 

“We support conservatives that are going to advance the core values that we advocate for and he has not convinced me,” Perkins said on Election Day. “Someone that has a track record of working against those core value is not someone that I’m interested in supporting.”

Perkins also added that he thought Cassidy would have a “hard time” winning unless control of the Senate hung in the balance. The GOP’s command over the body isn’t in jeopardy, but the Democratic Senatorial Campaign Committee has cancelled a portion of their ad buys for the runoff.

Maness is also joining Cassidy in a show of unity, his campaign said. Both men and their wives went on a double date Friday night in New Orleans and Maness will join Cassidy and Sen. Rand PaulRand PaulSenate Republicans reluctant to rush vote on healthcare bill Healthcare bill 'not the last step' to repealing ObamaCare, Republican says Rand Paul: 'If you offer me a 90 percent repeal, I'd probably vote for it' MORE (R-Ky.) for a campaign event on Monday in Baton Rouge.