Washington (CNN) A political newcomer knocked off Lexington Mayor Jim Gray -- a prized Democratic recruit and major figure in Kentucky politics -- in a primary for a US House seat Tuesday.

Amy McGrath, a retired Marine fighter pilot, won the Lexington-area 6th District contest and is now poised to take on Republican Rep. Andy Barr in a red-leaning district that Democrats hope will shift in their favor in November's midterm elections.

Gray conceded the race Tuesday night.

"I want to congratulate Amy McGrath on her victory and her win tonight," Gray said at his election night event. "It was a spirited campaign, and I know that Andy Barr is in for the fight of his life. I am ready to help Amy and I want all of you to join me. It's time for us to stand with Amy and continue this effort to do all we can to send her to Washington."

The win for McGrath is the latest evidence of a political climate in which voters are eager to cast out those they see as figures of the political establishment. It also showed the strength of female candidates amid the "Me Too" movement.

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