If Ken Paxton’s new pick for second-in-command is any indication, the Texas Attorney General won’t be backing down from his role as the state's top culture warrior anytime soon.

Jeff Mateer, tapped Wednesday by Paxton to be the state's first assistant attorney general amid a staffing shakeup, has built his career as a tenacious champion of religious expression in the public square. 

Mateer spent the past six years leading the legal team at the First Liberty Institute, where he burnished his conservative credentials going after — and sometimes defending — government entities engaged in disputes over religious liberty. 

His predecessor, Chip Roy, resigned Wednesday. Roy, who joined Paxton’s team when he took office last January, will now lead a super PAC supporting U.S. Sen. Ted Cruz’s run for the White House. 

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“The addition of Jeff Mateer as First Assistant Attorney General will have immediate impact on the agency with positive long-term effects that will strengthen our work for Texas for generations,” said Paxton in a statement announcing the hire. “Jeff brings a wealth of real-world experience as a seasoned trial and appellate attorney with broad and varied litigation experience spanning over 25 years of legal practice.”

A Paxton spokeswoman said Mateer was not immediately available for an interview. 

With Mateer’s counsel, the Plano-based conservative legal defense foundation has been involved in several headline-grabbing cases over the line between church and state. In 2012, it sued an East Texas high school for prohibiting cheerleaders from carrying banners displaying bible verses during athletic events. More recently, the group waged a battle against a local city ordinance extending anti-discrimination protections to include sexual orientation and gender identity.

Formed in 1997, the First Liberty Institute (which added “First” to its name in 2016) came to prominence in the early 2000s for pursuing what became known as the “Candy Cane Lawsuit" against a Plano public school that banned a student from distributing religious-themed candy cane pens. The case prompted school districts nationwide to address their own polices about religious expression — and, in Texas, a state law protecting holiday celebrations in schools from legal challenges. 

The issue of religious liberty has been a bright spot for Paxton during his first 15 months in office, while a looming criminal trial on three felony charges related to claims of financial fraud has largely diverted attention away from his public agenda.

The McKinney Republican has managed to continue making the topic a centerpiece despite his legal woes.

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During the 2015 legislative session, he helped generate support for legislation known as the Pastor Protection Bill, which affirmed the rights of clergy to refuse to conduct marriages that violate their beliefs.

Two days after the U.S. Supreme Court struck down same-sex marriage bans last summer, he gained the national spotlight and the praise of grassroots conservatives after issuing an opinion telling Texas county clerks with religious objections that pro bono lawyers were standing by to help defend them against legal challenges if they denied licenses to same-sex couples.

And, after a brief period out of the public eye following his indictment in late July, Paxton once again turned to the issue as a centerpiece. He launched a tour of churches and conservative groups around the state touting the need for more Christian voices in politics and government.

At one of those events in September, when he appeared before members of the First Baptist Grapevine church, Paxton indicated his ties to First Liberty go back to the start of his political career.

He credited the group’s executive director, Kelly Shackelford, with helping plant the idea that he should enter the race for the state House seat he won in 2002. 

“One of my opponents was my senator’s chief of staff, so he had all the endorsements of the community leaders, he had all the money,” Paxton said. “What I felt God was telling me was ‘get the Christian community out to vote.’”