Since he became Kamala Harris’s running mate, Tim Walz has attracted attention for his folksy charm, his life as a football coach and in the Army National Guard — and his innate ability, in a party that can seem stodgy and elite, to speak to Americans from any walk of life.

Less discussed, but plenty relevant, is his connection to an icon of Minnesota politics who today is no longer on the minds of many Americans. Had he not died in a plane crash 22 years ago, Paul Wellstone might still be in the U.S. Senate. Before Bernie Sanders rose to national prominence as a leader of the progressive left, there was Mr. Wellstone, the jovial maverick from Minnesota who campaigned in a clattering green school bus, turned up to campaign events in work shirts and jeans, and preferred staying in people’s homes to hotels.

As a senator, Mr. Wellstone was resolutely antiwar, pro-labor and supportive of the expansive social democracy that Franklin Roosevelt’s New Deal made possible. He belonged, first and foremost, to the legacy of left-of-center Democratic-Farmer-Labor Party senators who counted Eugene McCarthy and Hubert Humphrey among their leading lights.

Yet he was also one of a kind, pointing the way forward for a Democratic Party that would, in the last decades of the 20th century, fall prey to the siren songs of austerity and deregulation.

It is the Wellstone tradition of left-populism, once so central to the Democratic Party’s brand, that must be recovered. Elements of it have found something of a second wind in the Biden era. It was big government liberalism free of pretension and hectoring — stylistically unlike the sort found on both coasts — and never enervated by the academy. The airy language and exclusionary posture of the faculty lounge was not found in his earthy politics.

Mr. Walz’s presence on the presidential ticket is evidence, perhaps, that the Wellstone tradition might not get left behind in the 2020s, even as the billionaires who fund the Democrats demand policies that are much friendlier to them.