COLUMBIA, S.C. — Late Friday night, a few days and two states removed from the first Democratic debate, 21 of the 23 candidates for their party’s presidential nomination made nice. They posed, sweating through matching T-shirts, for pictures with Rep. James E. Clyburn (S.C.), who hosted them at his famous fish fry. Some threw arms around each other. Almost everyone shared laughs.

On Saturday, in front of a national television audience at the South Carolina Democratic Party Convention, none abandoned collegiality. They stuck to their stump speeches and avoided even polite infighting. But against that backdrop of peaceful coexistence, a few candidates tried to distinguish themselves from the pack.

In seven-minute speeches, the candidates staked out positions and made forceful arguments for their particular brand of leadership.

Sen. Kamala D. Harris (Calif.) made the most noticeable effort to stand out, abandoning her usual biographical stump speech for a more pointed and forceful explanation of why she is the right candidate .

For the first six months of her campaign, Harris had avoided referencing her fellow candidates unless asked. She almost entirely eschewed comparing herself with other Democrats, was relentlessly polite in her critiques of former vice president Joe Biden, who is leading in early polling, and was consistently absent in critiques of others in her party.

At her first event in Columbia on Friday afternoon, Harris began to throw stiff-arms by undermining arguments her fellow candidates made against Medicare-for-all and identifying hers as the most actionable of the gun-control policies. Saturday, a drum line led her down the escalator to a horde of supporters, the most attention-grabbing entrance of any of the candidates. She used part of her time onstage to argue that the Democratic nominee must not only be “a leader of our country, but we need a leader of our party.”

Harris also used her time to define her policy plan as “a 3 a.m. agenda” — a collection of plans to address issues that keep people up at night, as opposed to structural changes.

That positioned Harris in contrast with Sens. Elizabeth Warren (Mass.) and Bernie Sanders (I-Vt.), both of whom are known for their sweeping, system-altering visions, but also have drawn skepticism over their ability to enact those policies in the face of congressional inertia.

Former Maryland congressman John Delaney, one of the few members of the field who has shown a consistent willingness to criticize his competitors’ policies, also challenged the idea that those highflying policies are a useful approach.

“I don’t think what the American people need is more gridlock, more partisanship, and more ideology,” Delaney said. “ . . . We need to be the party that presents common-sense solutions, not impossible promises.”

Sanders used his first few minutes onstage to call out Third Way, a centrist Democratic group he calls “the corporate wing” of the party, whose conference last week spurred a Politico story about Warren’s potential as a “compromise candidate” between the middle of the party and the left.

“At this conference, I was called an existential threat to the Democratic Party. Why am I an existential threat?” Sanders asked, before positing that the systemic changes he promises would be a threat to establishment institutions.

Sanders made those comments near a man in a “No Old White Men 2020” shirt, a fitting representation of another divide that played out Saturday, as it might on the debate stage.

South Bend, Ind., Mayor Pete Buttigieg made his usual calls for a “new generation” of leadership, an implicit knock on Sanders and Biden, though not a new one. Former housing secretary Julián Castro did the same, as he usually does. But neither went out of his way to explicitly criticize Biden, Sanders or any of their elders.

Beto O’Rourke created the most theatrical speech of the event by standing on a platform in the middle of the room, rather than onstage, which left cameras focused on a backdrop of “BETO” signs and supporters. O’Rourke, who has struggled in recent polls, also deviated from his normal stump speech and quoted Robert F. Kennedy in a more emotional speech than usual, one that revived a sleepy late-afternoon crowd.

Biden seemed to launch his own counterargument against those wondering if his age may be a hindrance: He outlasted all of his fellow candidates at Friday night’s fish fry. He stayed until almost midnight, as if to challenge the idea that a 76-year-old can’t keep up.

Biden combated the notion again in his remarks Saturday, a disciplined rundown of his policy positions that included little editorializing. As he presented one of those positions — his health-care plan for a public option with a buy-in for those who can afford it — Biden raised another way in which he might soon find himself contrasting with some of his fellow candidates.

“We need to build on the Affordable Care Act,” said Biden, who was vice president when President Barack Obama’s administration pushed through that signature initiative. “Not jettison it.”

And as he avoided challenging his fellow candidates, Biden escaped the weekend without fielding any criticism, either. After a week in which Sen. Cory Booker (N.J.), Harris and others criticized Biden for his remarks about his work with segregationist Sen. James O. Eastland , no one brought it up with Biden on that stage Friday night. No one brought it up in their speeches Saturday, either.