Mr. Brown wasn’t listening to the crowd when he was basking in his win. He first noticed that he had become a meme when he checked Twitter, which he uses almost exclusively for tweeting about NASCAR, with the occasional mild joke thrown in, for his nearly 30,000 followers.

He thought it was kind of funny, and a couple of days later he tweeted the phrase, followed by, “*not political … just feelin myself.” He tried another line later that week: “To all the other Brandon’s out there, You’re welcome! Let’s go us.”

But the hot slogan of the American right doesn’t turn out to be something you can easily shake off. Now Mr. Brown finds himself facing a threat to his vocation: He’s an athlete on the cusp of breaking out in a sport that relies on corporate sponsors, a group that likes nothing less than the whiff of divisive partisanship.

“Our whole navigation is, you want to appeal to everybody, because, all in all, everybody is a consumer,” Mr. Brown said after our drive. “I have zero desire to be involved in politics.”