Barbara Boxer, a former California senator who spoke fondly of Mr. Biden, her onetime colleague, said she would “never tell other people what to do.” But underperforming candidates, she added, “ought to look at what their staying in the race means to the country, to the party and to their own reputations.” Ms. Boxer said she hoped to announce an endorsement on Sunday.
Many Biden-inclined voters have been less diplomatic. After the former vice president’s event in Spartanburg, S.C., on Friday evening, Antwion Yowe, 43, a local pastor, summoned a favored family analogy about separating standout options from the rest.
“My dad used to say: ‘barbecue and mildew,’” he said. “You’re either barbecue and you go forward, or you’re mildew and you’re done.” After South Carolina, he suggested, everyone except Mr. Biden and Mr. Sanders belonged in the latter camp.
Even if his peers were to fall away, Mr. Biden’s path would not be straightforward. Mr. Sanders has shown himself capable of building a formidable coalition, particularly in his blowout win in Nevada a week ago. He remains the favorite in California, the grandest delegate trove on the map. He has also flashed a victor’s swagger in scheduling events in the home states of two fellow hopefuls, which also happen to have primaries on Tuesday: Massachusetts, represented in the Senate by Elizabeth Warren, and Minnesota, the province of Ms. Klobuchar.
Any further setback for Ms. Warren could prove especially helpful to Mr. Sanders, potentially sending some of her progressive supporters into his camp. But voters do not always behave ideologically, a fact that cuts both ways for Mr. Sanders as Mr. Biden banks on a boost if other center-left candidates drop out: Some of that support will drift to Mr. Sanders even if voters do not align precisely with him on policy.
For one evening, though, Mr. Biden and his team seemed content not to dwell much on any of that. In Columbia on Saturday night, Mr. Biden — who has often campaigned in smaller venues — walked onstage to a raucous victory rally in a large gym. “We love you, Joe!” someone cried out.
“We can say, without fear of contradiction, the Bidens love you guys,” Mr. Biden replied. “The Bidens love you. That’s real.”