It seemed no accident that Mr. Biden quickly took his deal-making case from the swing state of Pennsylvania to Dubuque County, which flipped from the Democratic column to Mr. Trump in 2016, and sits in the middle of the densest stretch of counties in the nation that made the same shift to Mr. Trump.

Yet many on the left believe that Mr. Biden’s nostalgia for a bygone era of comity, compromise and civility — while appealing — is misplaced, or even naïve. They question whether historic pragmatism can even be considered pragmatic anymore in an era of norm-busting hyperpartisanship.

“Joe Biden knows better,” said Brian Fallon, a former top spokesman for Hillary Clinton and Senator Chuck Schumer, “because Joe Biden was the wingman for Barack Obama, who in his first year in his presidency had Mitch McConnell say his No. 1 objective was that Barack Obama wasn’t re-elected.”

Mr. Fallon acknowledged the political temptation to be “less partisan sounding,” by condemning only Mr. Trump in an attempt to appeal to disaffected Republicans. “I’m not saying a candidate needs to go around preaching doom and gloom,” he said. “But for the good of the country — beyond the short-term political calculus — we need someone who is cleareyed about the situation they will be inheriting if they win the White House.”

Some Democratic strategists point to Mayor Pete Buttigieg as a candidate who grasps the challenges to bipartisan deal-making. While he has offered rhetorical gestures to Republicans — casting himself as a consensus-seeking executive in a red state, Indiana — he has embraced more radical ideas that would help Democrats bypass the opposition party, such as eliminating the filibuster and stacking the Supreme Court with additional justices.

It took Ms. Warren only two days after the 2016 election to cast Mr. Trump as an outgrowth of an electorate demanding change. “The final results may have divided us — but the entire electorate embraced deep, fundamental reform of our economic system and our political system,” she said then.