WASHINGTON – Vermont Sen. Bernie Sanders' decisive win in the Nevada caucuses Saturday is forcing the Democratic Party to reckon with the strong possibility that a democratic socialist who views himself as fighting equally against the Democratic and Republican establishments will be the nominee.

“No campaign has a grassroots movement like we do, which is another reason why we’re going to win this election," Sanders said after he ran away with the caucuses.

His big win, after his capture of the popular vote in Iowa and New Hampshire, increases fears among some Democrats that a Sanders nomination could cost them both the White House and Congress.

And the results could further split the sharply divided party about the best way forward.

More moderate candidates were already fighting about who should step aside to allow one person to try to consolidate the vote against him.

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In combative remarks Saturday night, Pete Buttigieg said the only way Democrats can deliver on the progressive changes the party wants is with a nominee “who actually gives a damn about the effect you are having" on races from the top of the ticket to the competitive House and Senate races Democrats must win.

Buttigieg accused Sanders of ignoring, dismissing and even attacking “the very Democrats that we absolutely must send to Capitol Hill."

“Let’s listen to what they are telling us and support them from the top of the ticket,” said Buttigieg, who won more delegates than Sanders in Iowa and collected the same amount as Sanders did in New Hampshire. “It is too important.”

Former Vice President Joe Biden, who had entered the race with the strongest potential coalition – African Americans, white moderates and older voters – to defeat Sanders, was far behind in Nevada for the third contest in a row.

Biden appeared to knock both Sanders and former New York Mayor Michael Bloomberg Saturday, touting that he is a Democrat, “and I’m proud of it.”

“I ain’t a socialist. I ain’t a plutocrat. I’m a Democrat,” Biden said.

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Bloomberg has positioned himself to pick up Biden's mantle by spending a record amount of money in states that vote after the first four. But his widely criticized performance at Wednesday's night debate raised questions about whether he's up to the task.

Bloomberg's campaign manager issued a statement after Nevada's results, saying they reinforce the reality that a fragmented field is putting Sanders on pace to amass an insurmountable delegate lead.

"This is a candidate who just declared war on the so-called 'Democratic Establishment," said campaign manager Kevin Sheekey. "We are going to need Independents and Republicans to defeat Trump – attacking your own party is no way to get started."

Entrance polls indicate Sanders carried a strong lead among Latino voters, as well as running almost even with Biden with black voters. Biden, who placed second in Nevada, has enjoyed strong support from black voters for much of the primary season.

But recently, polls indicated Sanders has cut into that lead in South Carolina, and if the trend in Nevada holds in the Palmetto State, Sanders' dominance could continue.

In addition, voting has already begun in the delegate-rich states of California, where Sanders campaigned Friday, and Texas, where Sanders was Saturday.

"It sure looks like he’s the guy to beat," Democratic strategist Jim Manley said. "It’s clear if it wasn’t before that Sen. Sanders has a lot of momentum going into South Carolina and into Super Tuesday."

On MSNBC, Chris Matthews said the race was “pretty much over,” detailing the “dangers” that lie ahead in November.

Republicans "are going to kill him,” Matthews said. “I think it’s a little late to stop him, and I think that’s the problem."

One-third of the delegates are up for grabs when 14 states and one U.S. territory hold nominating contests on March 3. A candidate who emerges with a significant lead would be hard to catch.

"I've got news for the Republican establishment. I've got news for the Democratic establishment," Sanders tweeted Friday. "They can't stop us."

Sanders' anti-establishment battle cry is exactly why Lourdes Esparza, 38, of Las Vegas, who works two jobs, voted for him.

“He’s the best because he’s looking out for the people,” Esparza said. “He’s not establishment, he’s not status quo.”

Sanders was viewed as the favorite in Nevada – the state where, in October, he suffered the heart attack that could have ended his campaign – with most of the speculation centered on who would come in second.

The rest of the field needed a strong showing in the Silver State to give them a significant chance of having the energy and resources to keep their campaigns going into March.

In a memo posted Saturday by Axios, two of the co-founders of the center-left think tank Third Way urge the rest of the field to stand up to Sanders at next Tuesday’s debate. Otherwise, Jon Cowan and Michael Bennett write, they could doom the party – and the nation – to Trump and sweeping down-ballot GOP victories in November.

“Bernie Sanders is a socialist, and the political toxicity of his self-selected brand cannot be overstated,” they write.

A recently formed center-right group that opposes Trump had encouraged independents and disaffected Republicans in Nevada to vote in the Democratic caucuses Saturday to try to keep Sanders from getting the nomination.

“Extremists have taken over the Republican Party,” the group said in one of their ads in Nevada. “Don’t let the same thing happen to the Democrats.”

Buttigieg has already gotten more aggressive against Sanders. After going after Sanders in Wednesday’s debate, he started airing in South Carolina his first ad criticizing Sanders by name as he continues his attack on Sanders’ signature health care plan: "Medicare for All."

Sanders’ campaign accused Buttigieg on Friday of resorting “to the same lies about Medicare that we hear from Donald Trump."

In her final Nevada rally, Massachusetts Sen. Elizabeth Warren uncharacteristically criticized Sanders. She said he can't deliver the big changes he's promising when he opposes getting rid of the filibuster, the practice in the Senate that allows a minority of lawmakers to block legislation.

Center-left candidates had hoped Sanders' health care plan would hurt him in Nevada with the powerful Culinary Union. The union, which represents about 60,000 housekeepers, porters and bartenders working in Las Vegas casinos – warned members that "Medicare for All" would end the generous health care plans for which they had fought hard.

But while opposing the plan, the union chose not to put its considerable weight behind another candidate.

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Sanders swept Nevada’s most valuable precinct, the special caucus site set up at the Bellagio for Las Vegas casino workers.

By contrast, in 2016, Hillary Clinton won at all six caucus sites in casinos, helping her beat Sanders by 5 points overall.

Sanders' health care plan was one the top selling points for Sydney Fillippini, 23, a cancer survivor from Carson City who canvassed for Sanders.

"I'm tired of having a panic attack every month, worried that I won't have the medications that I need," she said. "This election is about the young in particular. Because it's our future on the line, so why not get involved and take control?"

Sanders built on his 2016 experience, turning his grassroots operation into a more polished team that still retained the enthusiasm.

Early entrance poll results showed Sanders trouncing the field among white and Latino voters and holding his own among black voters. He also was competitive among voters who described themselves as moderate or conservative because of his strong support from Latinos.

Nevada, the third state to vote, is the first with as significant minority population.

About three in 10 Nevadans are Latinos, 10% of the population is black, and 10% is Asian American and Pacific Islander.

Contributing: Jeanine Santucci, Ed Komenda and Marco della Cava, USA TODAY Network