Mr. Bishop has tied his hopes and his political identity to Mr. Trump and warned that a vote for his opponent would empower radical Democrats in Washington. His campaign has been running an ad featuring circus music and bobbling clowns wearing the faces of Mr. McCready and prominent progressives like Senator Bernie Sanders of Vermont and Representatives Alexandria Ocasio-Cortez of New York and Ilhan Omar of Minnesota, calling them all “crazy liberal clowns” who are “downright scary.”

“He’s enabled by the far left,” Mr. Bishop said of Mr. McCready.

The message appears to be resonating with conservatives in North Carolina, who say they have been alarmed by the vocal progressives who grab headlines and the liberal proposals that have come to the fore since Democrats took over the House last fall, including the idea of impeaching Mr. Trump and a vote over the summer to label his comments racist.

“I grew up as a Democrat, but when it gets to the point now that things are so far left, it takes away part of your choice,” said Bob Stone, 56, a telephone company employee from Wesley Chapel. “I hear them say that they’ll be an independent thinker when they’re campaigning, but every one of them that I see, after they get in, it’s all lock step and ‘Russia, Russia, Russia! Racism, racism, racism!’ It gets old.”

Mr. Bishop argues that his unapologetic support of Mr. Trump, who endorsed him via tweet in May, signals to voters who are looking for someone to back up the president that he is in line with their values.