Youngstown is the kind of blue-collar Midwestern stronghold where Mr. Trump’s struggling campaign must make a strong showing, particularly among white voters, if he is to have any chance of winning the presidential election. Broaching the topic of Mr. Trump on a street corner or bar stool here — and thus delving into matters of race, economics, immigration and the still-painful matter of the city’s disintegration — can be a volatile business.

“If you want to punch me in the face, do it,” Mr. Strines dared Mr. Wasko casually, after about 15 minutes of debate that played out under a billboard for a nearby adult novelty store called Sassy Sensations and touched on all of those issues.

Cars whooshed up and down Mahoning Avenue, past businesses shuttered or struggling, and past tired residential side streets now considered “food deserts” since the grocery store, a Sparkle Market, closed down about four years ago. Youngstown, a city of about 65,000 people, is about 60 percent smaller than it was in 1960. Decades ago, blacks, Irish, Italians and Eastern Europeans came to work among the great blast furnaces of the old mills. When those businesses closed between 1977 and 1982, tens of thousands lost their jobs.

Youngstown, as Mr. Springsteen noted in his 1995 song of the same name, once produced the iron and steel to fight America’s wars. It has also produced the boxing great Ray “Boom Boom” Mancini, a passion for high school football that rivals West Texas’, a tradition of political corruption — mostly the work of Democrats — and a long history, recently somewhat diminished, of mafia control. It is the rare small city whose past is dotted with car bombings, mob hits and characters with names like Moosey, Fats, Big Ernie and Brier Hill Jimmy.