Mr. Massie, who has not had a primary challenge since he was elected in 2012, conceded in an interview that he had allowed the flags to be displayed on his property. He said one of the construction workers had hung them in what he assumed to be “a little bit of a jab” at Mr. Massie for returning to Kentucky after having lived for several years in New England.
His “first instinct wasn’t to take it down — let them have their fun,” Mr. Massie said. But he added that he removed the flags after a dressing-down from his grandmother when she visited the house.
“She reminded me that her grandfather fought Union, and out of respect for her and my great-great-grandfather, I took it down,” he said. “In fact, she said, ‘That better be down the next time I come here.’”
As for Mr. McMurtry, Mr. Massie said: “I don’t know if I’ve ever called him a racist, but he’s promoting articles that say there’s racial disparity in I.Q. That’s a long stretch from a flag being displayed at a construction site.”
Even in Representative Steve King’s primary race in Iowa, in another predominantly white, ultraconservative district, his Republican challengers shied away from addressing his long history of racist comments. Instead, they glossed over the substance of his remarks and noted that they had led party leaders to strip him of his committee assignments, making him a less effective representative. Mr. King lost.
But in Kentucky, both Republicans have gravitated toward the issue of race and racism. The primary pits Mr. Massie, a fourth-term congressman known for his libertarian views and contrarian streak, against Mr. McMurtry, a lawyer who gained prominence when he represented a Covington Catholic high school student who sued CNN over its portrayal of an encounter at the Lincoln Memorial between young white men and a Native American man.
Mr. Massie has spent just under $1 million in the race to keep his job, while Mr. McMurtry has poured about $300,000 into the effort to unseat him, according to data compiled by the nonpartisan Center for Responsive Politics, making it the most costly House Republican primary in the state’s history.