When Donald J. Trump held a rally in Rome, Ga., in March, his audience included a second-generation supporter and first-time rallygoer named Luke Harris.

“My parents were always supporters of him — especially when he was going against Hillary,” recalled Mr. Harris, who was in sixth grade in Cartersville, Ga., when Mr. Trump defeated Hillary Clinton in 2016 to win the presidency.

Mr. Harris, now a 19-year-old student at Kennesaw State University, “just grew up looking at him, listening, watching him,” he said. “I kind of grew into it.”

Mr. Trump’s victory, to supporters and detractors alike, represented a profound break with politics as usual in the United States. People who voted against him feared he would turn the American presidency upside down. People who voted for him hoped he would.

But for the youngest Trump supporters participating in their first presidential election this year, Mr. Trump represents something that is all but impossible for older voters to imagine: the normal politics of their childhood.

Charlie Meyer, a 17-year-old high school student who volunteered at a Trump rally in Green Bay, Wis., last month, said he was first drawn to Mr. Trump at 13, during his presidency, because of his views on abortion, which resonated with his own as a Christian.