Georgia Gov. Brian Kemp announced on Wednesday that he has selected Republican donor and businesswoman Kelly Loeffler to fill the soon-to-be vacant U.S. Senate seat of Johnny Isakson.

Why it matters: In appointing Loeffler, Kemp is defying pressure from President Trump and other GOP leaders who have backed Rep. Doug Collins (R-Ga.), a staunch ally of the president who would be a lock to vote against removal in the event of an impeachment trial in the Senate.

The decision is likely to prompt backlash from some hardline conservatives, who have criticized Loeffler for donating to establishment Republicans like Mitt Romney and Paul Ryan.

Collins had previously signaled that he may pursue a primary against Loeffler in 2020 if he was not selected for the position.

Rep. Matt Gaetz (R-Fla.), another close Trump ally, warned on Twitter that Kemp himself may face a primary from a Trump-backed candidate as a result of the pick: "It’s not the establishment you are screwing with your donor-induced stubbornness. You are hurting President Trump. You know this because he told you.”

The backdrop: Trump told Kemp and Loeffler in a meeting last month that he wasn't sure how his supporters would respond to the choice and raised concerns about Loeffler's experience, according to Politico. Trump said during a tense exchange that he preferred Collins for the position and questioned why they were holding the meeting if Kemp had already made a decision, the Wall Street Journal reported.

Go deeper: