Among the many activists I’ve spoken with in recent weeks, racial justice organizers have been the most nonplused about liberals’ newfound sense of urgency. Many of the people they see taking stands against Mr. Trump are the same who have shown little respect for their issues and communities in the past. Rahm Emanuel, the mayor of Chicago, is a perfect example: He declared his city a “Trump-free zone” after the president’s decision to end the Deferred Action for Childhood Arrivals program. It might be good optics, but his mayorship has been anything but progressive on issues like policing, labor unions and schools.

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THE ELECTION HAS GALVANIZED activists of all kinds. After Hillary Clinton’s poor performance with working-class white voters, many on the left have realized that this constituency deserves more of its attention. I spoke recently to Kate Hess Pace, who founded Hoosier Action in her home state of Indiana, a membership organization for working-class Indianans who, with the decline of unions, have few ways of influencing politics. The group has brought members to Washington to lobby their senators on health care, among other actions. Ms. Pace says that most of the people she talks to in Indiana don’t hate Democrats or Republicans, but “outsiders,” people in Washington who have caused their state’s decline.

Some new members of the resistance may have people they can turn to easily for guidance: their kids. The radical movements calling attention to inequality and racism well before Mr. Trump’s election — from Occupy to the movement for black lives to a growing interest in socialism to the Dreamers protests — have been driven by millennials. And these movements are eager to grow.

There’s a reason that young people were taking up activism and protest years before “President Donald Trump” was a phrase anyone could imagine: Racism, sexism and inequality are nothing new. Mr. Trump’s election just ripped the polite veneer off American politics. In the process, I hope, he’s woken up a lot more people to the deep problems in our society.

“Many people that become deeply discontent with the status quo have some moment in their lives when all of a sudden they realize that what they’ve been taught are lies,” said Stuart McIntyre, a 27-year-old activist with the Ohio Organizing Collaborative, an umbrella group with much of the membership coming from black-led organizations in Ohio’s cities that has also seen an influx of new members since the election. “In my experience, a lot of people of color have that ‘mirror moment’ when they’re children. Among left-wing groups, a lot of people maybe have that moment in college. But for a lot of middle-class people, and for a lot of white Americans, that mirror moment is actually happening right now.” That’s a good thing.

“I’m looking for converts rather than for traitors,” Mr. McIntyre said. “I want our movement to be as big as possible.”