President Donald Trump and his political operation are working to unseat their first Republican incumbent: Kentucky Rep. Thomas Massie, who has drawn Trump's wrath by saying the president lacked the authority to attack Iran's nuclear sites without congressional approval and voted against his massive tax and spending cuts

Trump has appeared to reach a tipping point with the Kentucky Republican as Massie opposes the president’s legislative package and decision to bomb Iran without consulting Congress.

Here’s what to know about Thomas Massie, as Trump launches a campaign to oust one of his loudest intraparty critics from Congress.