In the most important elections of 2021, the center-left Democratic establishment has enjoyed an unbroken string of triumphs, besting the party’s activist wing from New York to New Orleans and from the Virginia coastline to the banks of the Cuyahoga River in Ohio. It is a winning streak that has shown the institutional Democratic Party to be more united than at any other point since the end of the Obama administration — and bonded tightly with the bulk of its electoral base.

These more moderate Democrats have mobilized an increasingly confident alliance of senior Black and Hispanic politicians, moderate older voters, white centrists and labor unions, in many ways mirroring the coalition Mr. Biden assembled in 2020…

Where some primary voters welcomed an angrier message during the Trump years, Mr. Jeffries said, there is less appetite now for revolutionary rhetoric casting the Democratic Party as a broken institution.

“The extreme left is obsessed with talking trash about mainstream Democrats on Twitter, when the majority of the electorate constitute mainstream Democrats at the polls,” Mr. Jeffries said. “In the post-Trump era, the anti-establishment line of attack is lame — when President Biden and Democratic legislators are delivering millions of good-paying jobs, the fastest-growing economy in 40 years and a massive child tax cut.”