SPRINGFIELD, Ohio—The blue and white “NOTICE” in the window at Schuler’s Bakery caused quite a stir when the owner put it up in November.

“This store is politically incorrect,” the sign read. “We say Merry Christmas, God Bless America. We salute our flag & give thanks to our troops, police officers and fire fighters. If this offends you, you are welcome to LEAVE.”

Trent Schuler, owner of the bakery founded by his grandfather in 1937, voted for Rep. John Boehner until the former House speaker quit in October. This November, he is backing the least Boehner-like candidate running for president: Donald Trump.

“At least I know I’m not getting more of the same,” Mr. Schuler said.

Mr. Boehner resigned from his Ohio seat, which he held for 24 years, under threat of a conservative revolt within his own party. What remains of the former House speaker’s legacy here could soon be swept away by forces unleashed by Mr. Trump.