Ryan Zinke said Monday that he will not run for reelection, becoming the latest Republican to step down ahead of a potentially difficult midterm cycle. In a letter announcing his decision, Zinke wrote that he had informed Donald Trump, the Montana governor, and senior GOP leadership of his choice.

Health concerns stemming from his career as a Navy SEAL were the primary reason, as multiple surgeries and upcoming treatments make it unlikely he could fully participate in future congressional sessions. Zinke said the injuries “are not immediately life threatening, but the repair cannot be deferred any longer,” and that recovery will require significant time with his wife, Lola Zinke, and family.

Zinke has represented Montana in Congress since 2015, aside from a break from 2017 to 2019 when he served as Secretary of the Interior under President Trump, resigning amid ethics investigations. His departure adds to a wave of more than 30 House Republicans who have announced retirements this cycle, further challenging the party’s narrow majority.