Another sign of the age: Chicagoland U.S. Rep. Dan Lipinski, one of the Democratic Party's final antiabortion holdouts, lost a primary election last week by 2 percentage points, or about 2,500 votes.

The traditional working-class Democrats who once chose Lipinski — and his father before him — used to be a keystone in the party's base.

But the left today tolerates no dissent on abortion. National progressives piled in to defeat Lipinski. Officially, the Democratic Party's apparatus supports its incumbents, but few bigwigs have gone out of their way to help Lipinski. Two years ago his fellow Illinois Congressman Luis Gutierrez called him "a dinosaur" and a holdover from the party of 1980, who should be "a relic in some museum."

Apropos enough, former Vice President Joe Biden spent decades opposed to taxpayer funding of abortion — until last summer, when he revised his values to fit the times.

Last week, Biden swept primaries in three states, carrying Florida by 39 points, Illinois by 23 and Arizona by 12, with some ballots still uncounted. In each state, he won men and women, whites and nonwhites, people with and without college degrees. Sen. Bernie Sanders is stepping back to "assess his campaign," his staff said mid-week.

Yet look at the exit polling of Democrats. Medicare for All registers 55% support to 33% oppose in Florida; 61% to 32% in Illinois; and 58% to 34% in Arizona. In President Barack Obama's old turf, Illinois, 43% say they want the nation's next leader to be more liberal than Obama.

Only 37% want a restoration of what Biden sometimes calls "our administration."

In remarks last week, Biden again reached out to progressives. "Senator Sanders and I may disagree on tactics," he said, "but we share a common vision." He directed a message to young Bernie voters: "I hear you. I know what's at stake. I know what we have to do."

When will Biden get around to reassuring moderates and independents?

It's Joe Biden's moment. But his agenda and Dan Lipinski's defeat show how fast the party is moving in Bernie Sanders's direction.

FROM AN EDITORIAL IN THE WALL STREET JOURNAL