Days after losing her re-election bid in deep red Utah, Representative Mia Love, the only black Republican woman in Congress, condemned President Trump on Monday in a scathing concession speech, describing him as having “no real relationships, just convenient transactions.”

She used similar language to attack her own party, accusing Republicans of having a “transactional” relationship with minority and black voters.

Ms. Love, who was elected to Congress in 2014 and had been viewed as a rising Republican star, lost her election by less than a percentage point to Ben McAdams, the Democratic mayor of Salt Lake County. Her defeat — in a district that Mr. Trump carried in 2016 by seven percentage points — handed Democrats another seat in the House of Representatives, giving the party 38 additional seats in the midterm elections and helping them take control of the chamber.

Ms. Love’s harsh words for Mr. Trump came in response to remarks the president made about her nearly three weeks ago: During a televised news conference the day after Election Day, Mr. Trump mocked the congresswoman for losing her race even as the votes were still being tallied.