WASHINGTON — Insurgent Republican primary candidates are trying to lay claim to President Donald Trump’s mantle — and knock out the establishment’s choices — as the GOP tries to defend a slim majority in the Senate and win races elsewhere.

In Nevada, endangered GOP incumbent Sen. Dean Heller drew a challenge Tuesday from businessman Danny Tarkanian, whose announcement on Fox News Channel seemingly aimed at an audience of one: the president himself.

Tarkanian criticized Heller as “one of the first never-Trumpers in Nevada” and argued he had obstructed Trump’s agenda in Congress.

The X factor now is what appeal Trump may hold— and what Trump himself will do. The president offered one clue Tuesday night, backing the establishment candidate Luther Strange in next week’s GOP Senate special election primary in Alabama.