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“The same reasons I decided to run in 2018 are still there,” Ms. McGrath said in an interview Tuesday afternoon. “My childhood dream was never to be a politician,” she said, but she and her husband “kind of looked at each other said we need better leaders in this country.”

Mr. McConnell is in some ways as loathed by Democrats as Mr. Trump. And he has arguably been more effective, maintaining a stronghold over the nation’s judiciary and largely refusing to cooperate with Democrats on major legislation.

In light of that, Ms. McGrath has adopted an unusual strategy for a Democrat: She is blaming Mr. McConnell for blocking legislation and cultural changes in Washington sought by Mr. Trump.

“Kentuckians voted for Donald Trump because they wanted to drain the swamp and lower prescription drug prices,” she said. “A lot of what has stood in the way of what Donald Trump promised is Senator McConnell.”