In March, shaken by the persistent controversy over comments pulled from the sermons of the Rev. Jeremiah Wright, an icon in Chicago’s black community and Obama’s former pastor, Obama gave his now famous speech on race. It was aimed, for the most part, at reassuring white voters over the Wright controversy, but it also marked the first time that he publicly addressed the generational divide his own campaign had exposed among black Americans. “For the men and women of Reverend Wright’s generation,” Obama said, “the memories of humiliation and doubt and fear have not gone away, nor has the anger and bitterness of those years. . . . At times, that anger is exploited by politicians, to gin up votes along racial lines or to make up for a politician’s own failings.” Some older black politicians may have recognized themselves in Obama’s subtle criticism, but those I spoke to said they took pride in seeing a black candidate articulate their experience to white America.

A lot of black incumbents who supported Clinton now find themselves trying to explain how they ended up so disconnected from their constituents, and many are preparing for their strongest primary challenges in years. (In a primary last month, John Lewis, who had run unopposed since 1992, had to beat not one but two primary opponents, including a 31-year-old minister named Markel Hutchins who designed his campaign to look just like Obama’s, right down to renting the same office space and using a red, white and blue logo in the shape of an “O.”) So far, incumbents facing insurrection over their endorsements of Clinton have easily dispatched their challengers, leading to a collective exhalation inside the black caucus in Washington. But then, as Jesse Jackson Jr. tried to remind his colleagues, the history of black politics is that such challengers are often heard from again.

On the first Tuesday in July, I traveled to Philadelphia, the site of Obama’s landmark speech on race, to see the city’s mayor, Michael Nutter. Known as a reformer during a 14-year stint on the City Council, Nutter played a central and intriguing role in this year’s presidential contest, emerging as the black face of Hillary Clinton’s campaign in Pennsylvania at a time when she desperately needed  and got  a solid victory in the state. Nutter certainly wasn’t the only visible black politician to campaign for Clinton deep into the primary season, but he was, in some ways, the least likely. Nutter is only four years older than Obama, Ivy League-educated, bookish and doggedly unemotional. He is, in short, the very prototype of the new generation of black political stars. But unlike Cory Booker or Artur Davis or Deval Patrick, the governor of Massachusetts, Nutter sided with Clinton, and he enthusiastically campaigned for her.

I was curious to know whether Nutter, who was elected to a four-year term just last fall, was bracing for the consequences of that decision. About 9 of every 10 black voters in Philadelphia pulled the lever for Obama, according to exit polls, and I heard at least one black Obama backer in Washington vow to make Nutter pay for his apostasy. On the day that I visited him at City Hall, his aides had been reviewing the video of a sermon from last fall in which a prominent black minister in the city suggested that Nutter might have a “white agenda.”

It was late in the day when Nutter and I sat down at a long conference table in his office, accompanied by the sounds of subway trains rumbling underneath and R & B music piped in from mounted speakers. He told me that he had made his decision methodically and had felt no pressure at all from his constituents.

Nutter said he sat down with both Clinton and Obama after his election as mayor and quizzed them about urban issues like housing, education and transportation. Race, he said, hadn’t entered into this thinking. He understood, he said, why the prospect of a black president after hundreds of years of discrimination was “powerful stuff” for a lot of his constituents, but he had a greater responsibility, and that was to run the nation’s sixth-largest city. “In the context of what I do for a living, I’ve not figured out a black or white way to fill a pothole,” he said, in a way that made me think he had said this many times before. Nutter was a delegate for Bill Clinton way back in 1992, and he said that the former first lady had shown a “depth of understanding” of what cities like Philadelphia were facing. It probably didn’t hurt that Obama endorsed one of Nutter’s opponents in last year’s mayoral primary, either.

Nutter said he wasn’t bothered by comments that the Clintons or their surrogates made during the campaign that had so incensed other black officials. “I think there was a lot of sensitivity, some warranted and some unwarranted,” he said. “It’s based on your life experience, and it’s generational. You know, if you have a sore on your arm, you don’t necessarily have to touch the sore to feel the pain. You can touch another part of your arm. You’ve still got a certain sensitivity to it. So if race is the sensitive thing, then anything that even gets close to it  sounds like it, looks like it, feels like it  is it.”