EAST GRAND RAPIDS, Mich. — Dave Levitt became a Republican after getting his M.B.A. in 1990. Like him, Republicans valued fiscal conservatism, balanced budgets and free trade, “all the things you learn in business school that are good and help people,” Mr. Levitt said.

These days, Mr. Levitt, a 55-year-old real estate developer, finds himself angry with President Trump and alienated from the party. It is an evolution shared by suburban voters nationally, particularly well-educated ones, like many of his neighbors in East Grand Rapids, Mich., an upscale suburb a few miles from downtown Grand Rapids.

Lindsay Kronemeyer, 28, lives about 15 miles further out in another suburb, Dorr Township. An observant Christian and passionate opponent of abortion, Ms. Kronemeyer was indifferent at first, but now could not be happier with Mr. Trump, a president who she says “is on our side.” Hers is a distinctly suburban story, too.

It just depends on which kind of suburb.

The political dividing line in America used to be between cities, which were mostly Democratic, and suburbs, which had long been Republican. But today it runs through the very center of the suburbs themselves, between a densely populated inner ring that is turning blue and a more spacious outer ring that is becoming ever more red.