Mr. Cameron, a former aide to Mr. McConnell, was expected to cruise to the nomination on the back of his ties to the powerful Senate minority leader and to Mr. Trump. But the race tightened after Ms. Craft, who is married to a coal billionaire, Joe Craft, began pouring millions of her own money into the race, flooding the airwaves with ads. Mr. Cameron did not have the resources to keep pace.
The bruising nature of the primary raised worries among some Kentucky Republicans about their prospects in the general election.
For nearly two months, Ms. Craft was the only major candidate with ads from her or her allies on broadcast television. Combined, she and her allies spent more than $7 million on advertising, compared with just $2.6 million by Mr. Cameron and his supporters, according to AdImpact, an ad-tracking firm.
Her campaign attacked Mr. Cameron for supporting the closure of a coal plant (the coal plant in question was in West Virginia) and rebuked him for not fighting the Justice Department’s investigation into the Louisville Police Department after police officers shot and killed Breonna Taylor during a botched raid on her apartment in 2020. She also sought to paint Mr. Cameron as a “follower” of Mr. McConnell, a rare public dig at a man who has guided Kentucky politics for nearly 40 years.
Mr. Cameron received a late boost from an allied political action committee, Bluegrass Freedom Action, which received most of its funding from the Concord Fund, which is part of a network of influential conservative groups managed by the activist Leonard A. Leo. The group spent $2.1 million in the final six weeks of the primary, aiding Mr. Cameron and attacking Ms. Craft.
In a special State House election on Tuesday, Republicans maintained power in the 108th Legislative District in north-central Pennsylvania as Michael Stender, a Republican school board member and a firefighter, was victorious in a three-candidate race, according to The A.P.
The safe G.O.P. seat opened up this year when Lynda Schlegel Culver, the longtime incumbent, resigned after winning a vacant seat in the State Senate.