Conservatives in North Carolina have not forgiven Sen. Thom Tillis for initially opposing President Trump’s border emergency, and the Republican could face a competitive primary in 2020 despite ultimately backing the White House.

Tillis voted against a Democratic resolution that would have blocked Trump from declaring a national emergency along the southern border. But grassroots Republicans back home are still fuming about the senator’s original plan to support the legislation on constitutional grounds. Sensing weakness after Tillis essentially flip-flopped, activists and some party officials are talking about fielding a primary challenger.