That famous Boston accent -- “pahk the cah in Hahvahd Yahd” -- is rare around Harvard Yard itself. Most professors and students come from elsewhere. So it was with some enthusiasm that I greeted those unmistakable flat A’s coming at me from a neighboring barstool at the joint I had slipped into before the start of a conference near Harvard. It was like sighting a rare bird in its native habitat. It was also an unexpected brush with a culture that, too often, is invisible to so many of us.

The man speaking was a guy around 30. He looked and talked remarkably like the actor Ben Affleck, who was raised nearby and effortlessly produces a rich Boston accent for his working-class film roles. Beside the man was a blond waitress with a permanent grin. She joshed with him, clearly a regular, and they swapped stories. It was a nice scene.

Then it took a bleak turn. They began talking about friends and family who had ruined or lost their lives to heroin or methamphetamine addictions. The waitress told a horrifying story of saving the life of her next-door neighbor, and mentioned almost casually that her younger sister had died at age 22 of an overdose. The man talked about his best friend becoming hooked, an addiction he was apparently still battling.

The bartender, an African-American woman originally from Phoenix, said she had learned on visits home how to deal with the many friends and acquaintances there who were using. “I hate to say it, but you know, it’s like in the zombie apocalypse. Once they go there, you have to cut them off entirely and have no contact anymore. Or else you get sucked in too.”

While one conversation in a bar doesn’t prove anything, the three people I encountered seemed emblematic of what is happening to too many Americans. They all had jobs, but the details of their lives seemed grim. They were on the fringes of the opiate and meth crisis that is chewing up the lives of the working class.

So it was with this dark vision in my mind that I went back across the street to the conference, which was entitled “Cities and Equity in the Era of the Trump Presidency” and was sponsored by the Lincoln Institute of Land Policy. The opening speaker was the economist and urbanologist Richard Florida, and he was talking about his new book, The New Urban Crisis.

The old urban crisis, Florida said, was about center cities and neighborhoods falling into disrepair, abandonment and poverty. The new crisis is about a small number of cities -- Boston, London, New York, San Francisco, Tokyo and a few others -- being too rich and leaving other cities and many of their own inhabitants behind. “This small group of elite places forges ever forward, while many -- if not most -- others struggle, stagnate or fall behind,” Florida writes in the book. “I call this process winner-take-all urbanism.”

Winner-take-all urbanism, according to Florida, produced the election of President Trump, as well as less-heralded events preceding it. The Newark, N.J.-born professor told about moving to Toronto, a city celebrated for its quaint neighborhoods and as the one-time home of the late urbanist writer and activist Jane Jacobs, only to see the election of Rob Ford as mayor. The ascent of Ford, the crack-using buffoon who won office on an anti-urban agenda that included ripping out bike paths, foreshadowed the election of Trump, Florida said. It was those left out of the new urban vision who voted for Trump in an effort to take back their cities and country.

Florida, of course, is hardly alone in noticing this emerging urban inequality: There were plenty of ideas at the conference for ways to begin countering it. Amy Cotter, who is leading the Lincoln Institute’s Legacy Cities Initiative, thought we should be encouraging young people to move to buzz-starved cities, places like Youngstown, Ohio. “People can find a quality of life and authenticity you can’t find elsewhere, and at an affordable price,” she said.

Mark Muro of the Brookings Institution described the tech industries -- successful though they might be -- as having “U-shaped job curves,” producing great wealth at the top end but low-paying service jobs at the bottom. He says that policies like guaranteed-income plans or government contributions to 401(k) plans could help to address this.

Florida proposed shifting money and power back to states and cities in a revival of the “new federalism” policy ideas of the 1980s. Many Republicans and conservatives have long favored this, and Florida thought that perhaps now might be the right time to try it.

For me, I believe it means looking at many issues that are not on liberal city agendas, such as the winner-take-all airline regulatory policies that have left many cities with poor air service and therefore a more difficult time with economic development. It means talking about more than just better transit, improved streets and a carbon tax.

On the last night of the conference I went back to the bar, and it was no longer the place of grim conversation that I had encountered before. This time it was full of happy, talkative people enjoying a few beers after a day of work or study. It was another reminder that we are in an era of two Americas, and that without more balance in our policies toward our cities we risk entering not a new urban age but a new Dark Age.