At a campaign event over the weekend, Mr. Biden, apparently undeterred by the union’s decision, cited his support from labor unions and then added, “I know in their hearts the Culinary Workers are there — in their hearts.”

Mr. Biden can still be unfocused at times, a problem that has hindered him throughout the race. During a rally in the Las Vegas suburb of Henderson on Friday evening, he declared that he did not want to use the teleprompters that had been set up for him, and later wound up talking to the crowd about Chinese land that is polluted with the metal cadmium. A minute later, he brought up an obscure government agency, the Defense Advanced Research Projects Agency, or DARPA. And a minute after that, his speech was over.

In those closing moments, he never mentioned the caucuses or explicitly asked attendees to support him.

But his time on the campaign trail in Nevada has also shown the promise of more diverse states. During a visit to a Black History Month festival on Saturday, he was greeted with enthusiasm by attendees as he made his way through the crowd. Before he spoke onstage, the M.C. referred to him as President Biden and offered to serve as the host at his victory party.

Mr. Biden was introduced by one of his newest endorsers, Mr. Horsford, who told the crowd that Mr. Biden “has our back” and added, “I know it because he had Barack Obama’s back as vice president for eight years.”

And so far, there is simply not the same kind of widespread criticism of his Nevada caucus organization that dogged him in Iowa. He has been aided by Yvanna Cancela, a state senator who is working as a senior adviser to the campaign, and Jennifer O’Malley Dillon, a former Obama campaign official who ran former Representative Beto O’Rourke’s presidential campaign and is assisting in a volunteer capacity.