Gov. Brian Kemp (R-Ga.) appointed Loeffler to the seat last year after a monthslong application process in which hundreds of candidates — including Collins — submitted their names for consideration.

Collins, who was President Donald Trump’s preferred pick for the appointment, said this month he was still considering running for the seat in 2020. Collins had reached out to the White House to take its temperature about a potential bid, according to one GOP official.

Collins has the benefit of being one of Trump’s staunchest allies on Capitol Hill. As the top Republican on the House Judiciary Committee, Collins played a leading role defending Trump from impeachment in the House. Collins was also tapped by Trump to serve as an impeachment surrogate during the Senate trial, allowing him to continue mounting a vigorous — and public — defense of the president.

Trump and his allies had pressed Kemp to appoint Collins, who they felt would be a reliable ally in the Senate. A handful of right-of-center groups had also come out against Loeffler, expressing concern that she lacked conservative credentials. And during a meeting at the White House late last year, Trump noted that Loeffler was not an original backer of his 2016 campaign and raised concerns that she had never held elected office before.

Appointed GOP Sen. Kelly Loeffler. | Russ Bynum/AP Photo

Kemp’s allies, however, praised the selection of Loeffler, hoping that she could help the party compete in suburban areas that have increasingly moved away from Republicans since Trump’s election. Senate Republicans, including Majority Leader Mitch McConnell, have rallied around their new colleague and pledged to back her in November.

And in an apparent bid to ward off any Republican challengers and demonstrate her campaign’s strength, Loeffler, a wealthy finance executive, pledged to pour $20 million of her own money into the race. Her campaign has already blanketed the Georgia airwaves with a TV ad in which she criticizes impeachment and portrays herself as a Trump ally.

Since coming to the Senate, Loeffler has been maneuvering to win over skeptics and solidify her conservative bona fides. She has signed on to several anti-abortion bills as well as a resolution dismissing the impeachment charges. And on Monday, she fired a shot at one of her GOP colleagues, bashing Sen. Mitt Romney, an outspoken Trump critic, via the president’s preferred mode of communication.

Romney “wants to appease the left by calling witnesses who will slander the @realDonaldTrump during their 15 minutes of fame,” Loeffler tweeted.

Burgess Everett contributed to this report.

