WASHINGTON — Amy McGrath, a retired Marine lieutenant colonel and combat pilot who was a star Democratic candidate in 2018 but failed to capture a House seat in Kentucky, announced Tuesday that she would seek to take on Senator Mitch McConnell, the Republican majority leader, for his seat in 2020.
Ms. McGrath, 44, made her announcement with a dark video denouncing Mr. McConnell, 77, who has served in the Senate since 1984 and has served as the central ballast for President Trump in Washington.
“Everything that’s wrong in Washington had to start someplace,” Ms. McGrath says in the video. “It started with this man who was elected a lifetime ago, and who has, bit by bit, year by year, turned Washington into something we all despise.”
She also reprised a story she used in her failed 2018 campaign against Representative Andy Barr, in which she recounts that as a young woman she wrote to Mr. McConnell “telling him I wanted to fly fighter jets in combat” and noting that he never wrote back.
Mr. McConnell, whose team has been anticipating Ms. McGrath’s announcement for months, responded with his own video with quotes culled from her House campaign, in which she expressed support for things like a single-payer health care system and abortion rights — positions he believes will be largely unpopular in his conservative state.
“Amy McGrath lost her only race in a Democratic wave election because she is an extreme liberal who is far out of touch with Kentuckians,” said Kevin Golden, a spokesman for Mr. McConnell’s re-election campaign.