Bernie Sanders has gotten farther than he probably expected when he launched his presidential campaign. No one, really, expected that he would come within a hair of matching Hillary Clinton in the Iowa caucuses and thoroughly dominate her in the New Hampshire primary. The Sanders campaign is revved up—and his support nationally is showing a dramatic uptick. Sanders now leads in one national poll—and Team Clinton is experiencing unexpected nightmares, all too reminiscent of 2008 when her frontrunner status was overturned by another challenger who excited voters with a promise of change.

But Saturday’s Nevada caucus promises to test whether Sanders’s appeal is broad enough to win in a state where the demographics are very different from Iowa and New Hampshire. Or, to flip the equation: Nevada is an ideal opportunity for Clinton to trip up Sanders, slowing his momentum before he has a chance to carry it into next week’s South Carolina primary and the Super Tuesday contests on March 1. 

Sanders’s surprising successes so far have come in two of the whitest states in America, both with large rural populations—the senator’s home court, in many ways. Having long served Vermont in Congress, Sanders is comfortable dealing with rural and small-town white constituencies. And he’s proven he can win over young, predominately white millennials—including young women

But Nevada offers a much different terrain: The state’s population is 28 percent Latino, 8 percent Asian-American, and 9 percent African-American. As University of Nevada political scientist David F. Damore notes in Politico, “The Las Vegas region, Nevada’s economic engine, is already majority-minority, and the state is expected to follow by decade’s end.” That’s a far cry from Manchester or Des Moines. 

Sanders needs to prove he can win over Latinos, Asian-Americans, and African-Americans—there’s no other way that he can seriously compete for the nomination. Clinton, conversely, needs to prove that her “firewall” of non-white support, which she’s also counting on in the upcoming Southern primaries, is going to be strong enough to block Sanders. 

Because it is a caucus state, polling in Nevada is tricky. As Donald Trump learned in Iowa, you can lead the polls, but voters new to the system aren’t always willing to show up for the complex rigors of caucusing—and Sanders, in particular, will be hoping to draw out young, first-time voters. But the polls that exist show a tight race, in essence a toss-up. The closeness of the race is remarkable given that Nevada had long been expected to be a Clinton cakewalk. 

Perhaps for this reason, the Clinton camp has been trying to tamp down expectations. Clinton press secretary Brian Fallon even argued on MSNBC that there are “reasons to believe that Senator Sanders should fare well in a state like Nevada. Obviously there’s an important Hispanic element to the Democratic caucus-goer universe in Nevada, but it’s still a state that is 80 percent white voters.” 

Not quite. The 2008 caucus turnout, when Clinton squared off against Barack Obama, was 35 percent non-white—and the non-white population has grown steadily in the state in the eight years since. Clinton had to walk back her staffer’s comments, saying, “I love Nevada, and Nevada was put into this early process because of diversity.” That diverse electorate gave Clinton a majority of the county delegates in 2008, even though superior organizing by Barack Obama’s team won him more national delegates (13 to Clinton’s twelve). Team Clinton therefore has a historical advantage in the state, and the campaign invested heavily—and early—in organizing to ensure that it can maximize the delegate count.

Sanders has been aggressive in courting young, working-class Latinos in Nevada. The state was especially hard hit by the Great Recession of 2008, and there’s evidence that Sanders’s message of economic populism is resonating. “It is clear to me when Mom is out working, Dad is out working and the kids are out working, wages in America are too damn low,” Sanders told a packed audience in Las Vegas at a recent rallyIt’s a message that has clearly helped him make headway in Nevada. 

Meanwhile, Nevada is a place where Clinton’s strategy of presenting herself as Obama’s heir won’t likely help her. It certainly doesn’t play well with young Latinos disappointed by the president’s failure to pass comprehensive immigration reform and by the massive number of deportations during his first term.

At times, Sanders’s full-throttle effort, especially intense in targeting unionized workers, has landed his campaign in trouble. BuzzFeed reporter Adrian Carrasquillo noted a telling example: “In late January, two Sanders staffers wore Culinary Union pins to gain access to employee-only areas in four hotels in an effort to persuade union members to support Sanders. The union was ‘disappointed and offended,’ leader Geo Arguello-Kline said at the time.” But this breach healed and the powerful Culinary Union, with its 57,000 members (more than half of them Latino) decided not to endorse a candidate—a blow to Clinton, who was expected to pick up the endorsement.

With its relatively few delegates, Nevada isn’t a do-or-die state—but its diversity does make it a bellwether state. If Sanders can pull off a win on Saturday, or even if he comes close, it’ll be clear that his revolution has real legs. Conversely, a strong Clinton victory would show that her firewall is still holding strong.