Zingers, Groaners and a Trump Pile-On: ‘That’s Called the Democratic Primary’

In certain moments — and Thursday supplied a few — it can be difficult to imagine any of the current front-runners transcending their liabilities to become the nominee. Can Mr. Biden, nostalgic and blunder-prone, really convince an anxious party that he is a man in tune with the times? Can the Brooklyn baritone of Mr. Sanders really move the masses to the political revolution he promises? Can Ms. Warren erase voters’ concerns, sometimes whispered even at her own rallies, about her general election viability?

“There’s just a real anxiety about not making a mistake,” said David Axelrod, the former chief strategist to President Barack Obama, citing the party’s angst about defeating Mr. Trump. “That may raise the sensitivity to people’s potential liabilities. But I think what campaigns are about in certain ways is to put these theories to the test and explore people’s strengths and weaknesses and see who emerges. In 2007, there still was this chatter about ‘can Obama actually win a general election?’”

Mr. Biden and the two progressive senators are making radically different bets on the electorate.

“There’s enormous, enormous opportunities once we get rid of Donald Trump,” Mr. Biden said in his opening, before pledging to build on the Affordable Care Act, unlike rivals who prefer a “Medicare for all” system.

“Let’s be clear,” Ms. Warren said in one exchange with Mr. Biden, joining Mr. Sanders in suggesting that the former vice president was not being bold enough, “I’ve actually never met anybody who likes their health insurance company.”

But the three do share some surface similarities as prospective opponents for Mr. Trump, aside from their age. They are all veterans of the public eye, their weaknesses familiar to many Americans. And they have all been underestimated at various points in this primary, their manifest campaign warts — Mr. Biden’s gaffe-making, Ms. Warren’s fraught history with Native American ancestry, Mr. Sanders’s competition from Ms. Warren for liberal hearts and minds — misdiagnosed as politically lethal.

For Mr. Biden and Mr. Sanders, a clash at center stage was perhaps inevitable. Over their decades in Washington, they have taken divergent paths to the top of Democratic politics.

Mr. Biden has played the unrepentant insider, firm in his belief that making change is a matter of gradual progress and warm relations with ideological foes. And Mr. Sanders has been the unkempt agitator, long convinced that his uncompromising liberalism would take hold through sheer force of organizing.