The young politician gave the most important speech of his life Tuesday night at a vocational school in a working-class town in front of a Ford Mustang that screamed "old manufacturing economy." He spoke for unity across regional and racial lines — "the mechanic in Pittsburgh and the teacher in Tulsa and the daycare worker in Birmingham" — in support of economic fairness and against those who conquer by sowing division.

Oh yes, and the 37-year-old's last name is Kennedy.

Rep. Joe Kennedy seemed ideal to deliver the Democratic response to President Trump's State of the Union address. And his selection of Fall River, Mass., as his venue sent a welcoming signal to the party's lost souls. While Hillary Clinton won the city in 2016, deep economic discontent allowed Trump to up the GOP's share by 11 points. Kennedy brought with him his family's tradition of confronting dividers on behalf of a diverse alliance, a role Barack Obama famously played 14 years ago.

"Bullies may land a punch," Kennedy declared. "They might leave a mark. But they have never, not once, in the history of our United States managed to match the strength and spirit of a people united in defense of their future." The vigorous nods this generated in Democratic living rooms around the country could probably power Fall River for a decade.

But it shows how much politics has changed that choosing Kennedy to carry the torch was controversial. For younger generations, "Kennedy" as a concept is so five decades ago. He is a white guy with ginger hair speaking for the party at a moment when African-Americans, Latinos and women are in the ascendancy in the Democratic coalition. Its members differ sharply over whether they should even try to bring home white working people who strayed to Trump. Many want to forge a new majority without them.

I cannot pretend to metaphysical neutrality on this question because I grew up in Fall River a relatively well-off (by local standards) kid in a blue-collar town perpetually on the wrong end of whatever economic trends were lifting up people elsewhere. I have never stopped loving a place that shaped so much of who I am and what I believe.

My family was conservative in a New Deal stronghold, but even conservatives imbibed a labor, ethnic and largely Catholic culture that nourished a rough-and-ready kind of liberalism. One sign of the pervasiveness of this worldview: My loyally Republican dad once surprised me by saying that had he been unemployed in the 1930s, he would have joined most of the rest of our town in voting for FDR.

My own politics were forged by the Vietnam War and civil rights, particularly after a transformative engagement with the writings of Martin Luther King Jr., in a religion class in high school. But as important was the personal — a gut instinct to side with blue-collar friends, neighbors, union folks and fellow parishioners who grew accustomed to getting knocked around by the economy.

I could never worship the free market because I respected too many people it regularly left stranded. In Fall River, "solidarity" is a living, breathing concept. So for me, it would be as wrong to abandon the white working class as it would be to break faith with African-Americans, Latinos, members of the LGBTQ community and women of all classes struggling for justice.

The only political coalition that makes sense is an alliance of everybody who believes in government policies and an economic system that meet the standard Kennedy set: "We are all worthy, we are all equal, and we all count."

Kennedy, it would appear from the commentary, won over many who were skeptical of him going in, partly because he was so insistent on making clear that a belief in the Fall River-style Democratic Party of old in no way precludes standing up for Dreamers, Black Lives Matter and #MeToo. He helps his personal cause by wearing his name lightly. He noted in an interview on Wednesday that while his forebears were "pretty good at giving a speech," he approached the evening with a modest objective. "I set the bar at not destroying my political career," he said with a chuckle. He managed that.

The long-term test of his effort will be whether he succeeded in persuading his party's battling factions that a politics of false choices and zero-sum games is neither progressive nor effective. As a son of Fall River, I hope he did.

— E.J. Dionne's email address is ejdionne@washpost.com. Twitter: @EJDionne.