In December 2022, early into what he now describes as his political journey, Senator Chris Murphy of Connecticut gave a speech warning his fellow Democrats that they were ignoring a crisis staring them in the face.

For over a year, President Biden and his allies had been promoting data showing an economic miracle, as friendly pundits described it — a record-setting stock market, low unemployment and G.D.P. growth outpacing that of almost every other Western nation. But very few voters believed the story those metrics were telling. In poll after poll, they expressed a bleak view of the economy — to the frustration of both Democrats and many economists.

Mr. Murphy thought he knew why. “The challenges America faces aren’t really logistical,” he told the crowd. “They are metaphysical. And the sooner we understand the unspooling of identity and meaning that is happening in America today, the sooner we can come up with practical policies to address this crisis.”

The subject of the speech was what Mr. Murphy called the imminent “fall of American neoliberalism.” This may sound like strange talk from a middle-of-the-road Democratic senator, who up until that point had never seemed to believe that the system that orders our world was on the verge of falling. He campaigned for Hillary Clinton against Bernie Sanders during the 2016 primaries, and his most visible political stance up until then was his work on gun control after the Sandy Hook shooting.

Thoughtful but prone to speaking in talking points, he still comes off more like a polished Connecticut dad than a champion of the disaffected. But Mr. Murphy was then in the full flush of discovering a new way of understanding the state of the nation, and it had set him on a journey that even he has struggled sometimes to describe: to understand how the version of liberalism we’d adopted — defined by its emphasis on free markets, globalization and consumer choice — had begun to feel to many like a dead end and to come up with a new vision for the Democratic Party.

As the Democrats gather for their national convention this week, with Kamala Harris as their candidate for president, the party has a long way to go toward confronting the crisis Mr. Murphy sees.