LAS VEGAS — Senator Bernie Sanders claimed a major victory in the Nevada caucuses on Saturday that demonstrated his broad appeal in the first racially diverse state in the presidential primary race and established him as the clear front-runner for the Democratic nomination.
In a significant show of force, the progressive Mr. Sanders was leading his nearest rivals by a significant amount in early tallies, and The Associated Press named him the winner on Saturday evening.
His triumph in Nevada, after strong performances in Iowa and New Hampshire, will propel him into next Saturday’s primary in South Carolina, and the Super Tuesday contests immediately thereafter, with a burst of momentum that may make it difficult for the still-fractured moderate wing of the party to slow his march.
Mr. Sanders’s success, and the continued uncertainty over who is his strongest would-be rival, makes it less clear than ever how centrist forces in the party can organize themselves for a potentially monthslong nomination fight. The moderate wing is still grappling with an unusually crowded field for this late in the race, no clear alternative to Mr. Sanders and no sign that any of those vying for that role will soon drop out to hasten a coalescence.
As results were being counted on Saturday night, former Vice President Joseph R. Biden Jr., former Mayor Pete Buttigieg of South Bend, Ind., Senator Elizabeth Warren of Massachusetts, the billionaire investor Tom Steyer and Senator Amy Klobuchar of Minnesota were all competing for what would clearly be a distant second place finish.
The fragmentation of the vote among all of those candidates, not only in Nevada but in the coming primaries, is likely to strengthen Mr. Sanders. After the split decision in Iowa, where he shared the lead with Mr. Buttigieg, and a modest victory in New Hampshire, he proved his ability to win convincingly in a more diverse state, an outcome that often eluded him in his 2016 bid for the Democratic nomination.
With its mix of Hispanic, African-American and Asian-American voters, Nevada offered Mr. Sanders a rejoinder to critics who claim he cannot broaden his appeal beyond his base of white liberals.
Mr. Sanders’s steady progress in the primary contest has come amid widespread grumbling and occasional howls of alarm from the Democratic establishment, which views Mr. Sanders — a 78-year-old democratic socialist from Vermont who has never joined the party — and his movement with a combination of fear and distrust. The anxiety deepened this weekend in the aftermath of reports that government intelligence officials believe the Russian government is aiding his candidacy, and after Mr. Sanders acknowledged that he was briefed on the Russians’ apparent intervention a month ago.
Yet his coalition in Nevada — where 35 percent of the voters were not white, according to entrance polls — bodes well for his prospects in the 15 states and territories that will vote on the most important day of the race in just over a week. The March 3 contests include large, diverse states such as California, Colorado and Texas, and the delegate lode is so hefty that if Mr. Sanders performs well, it will be difficult for one of his rivals to catch up given the unflagging dedication of his supporters
Making that task more difficult is that the more moderate candidates continue to split votes and, more important, show no signs that they are ready to drop out of the race. They all seem determined to forge ahead either by using their own fortunes or by raising enough money from donations to proceed. That was evident on Saturday, as candidates like Ms. Warren, Mr. Buttigieg and Ms. Klobuchar, as well as Mr. Sanders, traveled to rallies in states that will cast ballots on Super Tuesday. Mr. Biden appeared at a Las Vegas union hall while most votes were still uncounted to claim a comeback and vowed victory in South Carolina.
“Y’all did it for me,” he told supporters, trying out a new line aimed at his rivals. “I ain’t a socialist, I ain’t a plutocrat, I’m a Democrat.”
At the same time, his campaign asserted that Mr. Biden would finish in second place here, a claim challenged by Mr. Buttigieg’s aides.
Even as many of the candidates left the state, Nevada retained the political spotlight as the caucuses appeared to run relatively smoothly after the debacle in Iowa this month.
Democrats in this state made drastic changes to their own caucus procedures after Iowa, scrapping the software they had been planning to use and intensively training thousands of people to pre-empt problems. There were scattered reports of volunteer shortfalls at some precincts, though not on a scale that seemed to alter the contest in any appreciable way, and some precincts had problems getting through on the telephone hotline to report caucus results, prompting the state party to add phone lines.
More revealing than the caucus process was who voted — and the coalition that Mr. Sanders built in a state that derailed his then-promising candidacy four years ago.
He simply dominated the state, winning men and women, union members and nonunion workers, and those who attended college and those who did not, according to entrance polls of caucusgoers.
The Vermont senator not only won among self-described liberal voters, but also made inroads with moderates for the first time. Among self-described moderate or conservative caucusgoers, Mr. Sanders was the top vote-getter, albeit narrowly: He captured 25 percent of such voters, while Mr. Biden won 23 percent, according to entrance polls.
That was in part because many black and Hispanic voters described themselves as moderates, and because Mr. Sanders outpaced the field with Hispanics, taking 53 percent, and was second only to Mr. Biden among African-Americans.
He made less progress with older voters, whom he has repeatedly struggled with, but claimed new evidence that his calls for “a political revolution” were motivating new voters. He won voters under 30 with an extraordinary 66 percent, and dominated among the broader universe of voters who said they were attending their first caucuses, a demographic that made up just over half of the electorate.
Mr. Sanders’s performance will echo beyond Nevada and surely focus the minds of his rivals, some of which were already sounding an alarm while votes were still being cast Saturday.
“We could wake up in 10 days with Senator Sanders with a prohibitive lead or we could wake up on the road to a unified party,” Mr. Buttigieg told a handful of reporters and photographers who trailed him around a high school at the edge of Las Vegas, where Democrats assembled to cast their ballots.
Asked before the results were announced how he would slow Mr. Sanders’s march should he triumph here, Mr. Biden, stopping at a caucus site in North Las Vegas, said: “I beat him by going to — just moving on. People want to know who’s the most likely to beat Donald Trump. And even the few polls that show Bernie tied with me, or ahead of me, show me being the one that is most likely to be able to beat Trump.”
Mr. Biden emphasized the importance of keeping the Democratic majority in the House of Representatives and taking back seats in the Republican-controlled Senate, and noted that he had raised “over a million bucks” since the debate on Wednesday.
Ms. Warren raised considerably more than that since her standout performance. In fact, her campaign said on Saturday that it had brought in $14 million in the 10 days after the New Hampshire primary. That could be enough to sustain her in the race through Super Tuesday, a prospect that seemed unlikely after her dismal finish in New Hampshire and given the money crunch she was in before the race there.
On Saturday, Ms. Warren stopped by a high school in Henderson, Nev., just outside Las Vegas, armed with Dunkin’ Donuts for caucusgoers.
A man thanked her for taking on the most prominent candidate not on the ballot here: Michael R. Bloomberg, the former mayor of New York City, who is not competing in any of the early states. “As a former New Yorker, I’d like to say thank you for what you said to the mayor,” he said, alluding to Ms. Warren’s searing criticism of Mr. Bloomberg at the debate.