Advisers to three rival campaigns privately conceded over the weekend that the best anyone else could hope for here is second or third. Some of them gape at the crowd sizes at Sanders’ events — like the swarm of supporters who accompanied Sanders, his fist raised, to an early caucus site in Las Vegas on Saturday, the first day of early voting in the state.

While few expect that Sanders can carry more than a third of the vote in Nevada, nearly everyone believes that will be enough to win in a field where the moderate vote remains splintered. It is becoming a source of celebration for Sanders’ supporters and an urgent problem for those who want to prevent him from claiming the nomination.

“He’s going to win with 28 percent of the vote. We’re not talking about him getting 50 percent of the vote,” said Andres Ramirez, a Nevada-based Democratic strategist and former vice chairman of the Democratic National Committee’s Hispanic Caucus. “But the rest of the field is so fragmented, and he has his base locked, that he can continue winning just by holding onto his base.”