Jim Young / Reuters

Senator Bernie Sanders endured nail-biters in Iowa and New Hampshire. Today, Nevada voters handed him a landslide victory.

Sanders’s dominant victory in the Silver State solidifies his standing as the front-runner for the Democratic presidential nomination, giving him and the progressive movement a clear boost as the race heads to more challenging territory in South Carolina and then across the country on March 3—Super Tuesday.

Although Nevada, like the first two Democratic nominating contests, sends relatively few delegates to the party’s national convention this summer, Sanders’s win demonstrated two key things. First, the democratic socialist from Vermont has significantly improved his performance from 2016 among a more diverse primary electorate; just 66 percent of caucus-goers in Nevada were white and more than one-quarter were Latino or black, according to entrance polls. That change could prove crucial as Sanders tries to rack up delegates in huge states like Texas and California on Super Tuesday. Waiting for him in March is former New York Mayor Michael Bloomberg, who is hoping that an unprecedented barrage of television ads will drown out his roundly criticized debate debut last week.

Second, while former Vice President Joe Biden, Senator Amy Klobuchar, and former Mayor Pete Buttigieg again split the moderate vote, Sanders has—at least for now—consolidated the left wing of the Democratic Party behind him. Senator Elizabeth Warren’s forceful performance in Wednesday’s Las Vegas debate came too late to matter in Nevada, where well over half the caucus electorate—some 75,000 people—had already voted early. Entrance polls did show Warren doing well (though still behind Sanders) among the 15 percent of voters who made their decision in the past few days. She’ll need another strong showing at next week’s debate in South Carolina if she hopes to compete seriously with Sanders there and in many larger states on Super Tuesday.

Biden finished far behind Sanders, clustered with Buttigieg, the billionaire activist Tom Steyer, and Warren. The former vice president is banking on a victory next Saturday in South Carolina to keep his campaign afloat, but that may depend on how much momentum Sanders carries out of Nevada.

If Sanders slightly underperformed expectations in Iowa and New Hampshire—where he still came out with a win and at worst a tie—Nevada illuminated the durability of his support. A fight between his campaign and the leadership of the powerful union of culinary workers over Sanders’s Medicare for All proposal did little to diminish his standing among laborers. He fared well among union members in entrance polls, and he won caucus precincts at major Las Vegas casinos dominated by culinary workers.

Nevada is also significant in that it represents the first state where Sanders improved his position from 2016, when he lost the caucus handily to Hillary Clinton. His biggest challenges are yet to come, as Biden tries to regroup in South Carolina, Bloomberg’s billions swamp the airwaves, and the party establishment frets about the prospect of a democrat socialist leading its ticket in the fall. The candidates who largely laid off Sanders in favor of demolishing Bloomberg at last week’s debate might now target him instead. Sanders’s critics will point out that collectively, moderate candidates outpoll the Vermont senator and that he remains unlikely to win a majority of pledged delegates heading into the Democratic convention in Milwaukee.

That may be true. But while the question of whether a candidate as far left as Sanders can defeat Donald Trump and win the presidency remains, it is becoming more and more clear which wing of the Democratic Party is prevailing: In the most diverse contest of the year, the most progressive candidate in the field won his biggest victory yet.

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