Rep. Doug Collins (R-GA), one of President Donald Trump’s most vocal defenders against the Democrats’ impeachment effort, announced Wednesday that he will challenge recently-installed Sen. Kelly Loeffler (R-GA) in a Georgia primary battle this year.

“For months, I have given serious deliberation to the role I should serve that would best benefit GA, the country and @realDonaldTrump. Today, I have officially launched my campaign for Senate to do just that,” Collins wrote on Twitter, along with a fundraising link for his newly-launched campaign.

For months, I have given serious deliberation to the role I should serve that would best benefit GA, the country and @realDonaldTrump. Today, I have officially launched my campaign for Senate to do just that. I invite you to join our campaign here:https://t.co/xubaYUr5RP — Doug Collins (@CollinsforGA) January 29, 2020

President Trump lobbied Georgia Gov. Brian Kemp (R) to appoint Collins to the seat after Sen. Johnny Isakson’s (R-GA) retirement due to ongoing health issues. Instead, Kemp defied the president in December by selecting Kelly Loeffler, a businesswoman and Republican donor with deep ties to the party’s establishment wing.

The move sparked ire from the president’s staunchest allies, including Rep. Matt Gaetz (R-FL), who said Kemp had ended his political career by nominating Loeffler over Collins. Conservative radio host Mark Levin piled on the criticism, calling Loeffler a “RINO” — an acronym for a “Republican In Name Only.

Almost immediately after Collins’ announcement, the National Republican Senatorial Committee issued a statement opposing the Republican congressman’s bid and warned a primary fight puts the Peach State’s Senate seats in play.

“The shortsightedness in this decision is stunning. Doug Collins’ selfishness will hurt David Perdue, Kelly Loeffler, and President Trump. Not to mention the people of Georgia who stand to bear the burden of it for years to come,” said NRSC executive director Kevin McLaughlin. “All he has done is put two senate seats, multiple house seats, and Georgia’s 16 electoral votes in play. The NRSC stands firmly behind Sen. Kelly Loeffler and urges anyone who wants to re-elect President Trump, hold the GOP senate majority, and stop socialism to do the same.”

Loeffler, nor her office, have responded to Collins’ announcement.