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

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

Trump appears to have reached a tipping point with the Kentucky Republican, who opposes the president’s legislative package and decision to bomb Iran without consulting Congress.