Supporters cheer for Sen. Bernie Sanders (VT) during a rally Tuesday at the Scope Arena in Norfolk. (Jonathan Newton/The Washington Post)

Jennifer Schultz didn’t realize how popular Sen. Bernie Sanders (Vt.) had become here until she didn’t endorse him. In late January, when Sanders brought his presidential campaign to Duluth, Schultz, a Democratic state representative, wrote a quick Facebook post welcoming him to northern Minnesota. Welcoming, not endorsing. Just being nice.

That wasn’t how her constituents read it.

“It was shared, like, 8,000 times,” Schultz said. “I was amazed by that — by thank yous rolling in for something I didn’t even say.”

That, and the subsequent rally of 6,000 cheering voters, convinced Schultz that Sanders had started to conquer Minnesota. “It seems like Bernie’s doing better than Hillary here,” she said. “I think Trump and Bernie are both doing well, because you’ve got a lot of people who are low income and feel left behind.”

The flip side of Hillary Clinton’s triumph with black voters in the Nevada Democratic caucuses Saturday was her weakness among whites. For the third time, she lost an electorate that had backed her strongly in 2008. Although Clinton is building toward an expected win in South Carolina this weekend, her vulnerability with white voters could reappear three days later, on Super Tuesday, when the primary contest moves to 11 states, including Minnesota. Even more states come after that with large populations of union members and people who lack college degrees.

The evening before the Democratic Nevada caucus, former Secretary of State Hillary Clinton spoke to an excited outdoor rally crowd in Las Vegas. (Melina Mara/The Washington Post)

Clinton’s strategy in the March 1 contests is to win landslides among black voters in the South. But there are no Southern primaries after March 15. Before the race gets to Clinton’s home state, New York, it runs through Idaho, Utah, Alaska, Washington, Wisconsin and Wyoming.

Her campaign will not be caught sleeping in Minnesota — but that may not be enough to surmount Sanders’s advantage here. She drew hard lessons from 2008, when Barack Obama won the caucuses in a landslide. She sent a full-time state director to Minnesota in the summer of 2015 and opened four offices; she booked TV time in advance of March 1.

If there was a place where Clinton’s message of building on the Obama legacy might click, might make converts, it was surely Minnesota, where unemployment had sunk below 4 percent and health-insurance coverage had reached 95 percent. It was surely Duluth and the Iron Range, with its critical mass of white, working-class voters holding union cards.

But that doesn’t appear to be happening. Instead, many voters are skeptical of just how good the Obama years have been for them. And they are disappointed in what they see as Clinton’s less-ambitious ideas about what is possible.

“I don’t want to say anything negative about Hillary Clinton, because she’s not a bad candidate,” said Sharla Gardner, a former Duluth city council member who is now running for the state Senate and who backed Clinton at first. “But she’s not the best candidate. She doesn’t start from a place of can-do. Her campaign is ‘No, we can’t,’ and that attitude is actually harming the working poor. It’s forcing the working poor to buy insurance policies they can’t afford, because the deductibles are so high.”

Sanders’s buzzer-beating loss in Nevada revealed the limitations of his appeal, notably among minorities, who chose Clinton 76 percent to 22 percent, according to entrance polling reported by CNN. And it’s unclear how much more momentum a Clinton win in South Carolina would give her heading into Super Tuesday.

On Feb. 20, Democratic presidential candidate Hillary Clinton thanked supporters for her win in Nevada while rival Bernie Sanders predicted victory for his campaign at the Democratic National Convention in July. (Sarah Parnass/The Washington Post)

But Minnesota’s rapid transformation into a battleground echoes another thing that happened in Nevada: White voters there went for Sanders by two points; white voters who lacked college degrees went for him by eight points. Working-class voters who seemed friendly to Clinton are now seen as locked in for Sanders. Jeff Weaver, Sanders’s campaign manager, describes Minnesota as the place where the candidate will start winning the industrial Midwest.

“We’ve gone from possibility to probability,” said Rep. Keith Ellison (D-Minn.), who represents Minneapolis and is one of just two federal legislators to endorse Sanders. “We’ve gone from ‘We hope, we pray, maybe, maybe’ to ‘Hey, we can do this.’ I mean, there were a lot of people who believed in everything Bernie was saying but didn’t believe he could win. Now, he’s neck-and-neck in national polls.”

In Minnesota, like Nevada, the late-building Sanders campaign now has more offices than Clinton — six — and is more visible on television.

“Bernie’s really popular up in the range, super-popular,” said Rep. Rick Nolan (D-Minn.), who came out of retirement in 2012 to win the district that includes Duluth and the Iron Range. “He projects an authenticity that resonates with the people who’ve grown up there.”

For months, the unofficial street team for Sanders was Twin Ports for Change, activists working in Duluth and the Wisconsin border town of Superior. The group was run by Mike Kuitu, a 59-year-old retired operating engineer, who would gather activists together in the bar above the Duluth AFL-CIO hall.

“We tend to be born with a little bit of glass in our guts around here,” said Kuitu, by way of explaining Sanders’s appeal. “I’d say northern Minnesota is one of the last holdouts of labor liberal politics.”

If everything was going Clinton’s way, those voters would see her as the next step in a change campaign that was clearly working.

“Duluth in some ways is the epitome of the accomplishments of the Obama years,” said Joel Sipress, a city council member. “This city, which was hit hard in the 1990s, has finally found its bearings. That’s all great and there’s optimism, but half the workers here don’t have paid sick leave. A lot of us were sort of resigned at Hillary being the candidate — not thrilled, but accepting.”

The disconnect was evident at the previous week’s Democratic-Farmer-Labor Party dinner, down in St. Paul, where every major statewide officeholder grabbed a microphone to endorse Clinton. Gov. Mark Dayton (D), a workmanlike politician who served one Senate term alongside Clinton, asked Democrats to consider all the incremental changes they’d made because they settled for him: same-sex marriage. Universal pre-kindergarten.

“I wish you could see the Hillary Clinton that I know,” Dayton said. “I wish you could see how she has fought again and again. Then I remember how some people thought I wasn’t progressive enough when I ran for governor in 2010. In fact, some of them even locked me out of the state convention — literally, locked me out of the convention hall! Fortunately, we united together that fall. Otherwise a Republican governor would have been elected and signed all those bills that I vetoed.”

This is the argument for continuing the Obama years; it assumes they were successful — and for some, that’s a leap. At a Thursday gathering of Sanders supporters, they shared story after story about how the safety net they were supposed to be so grateful for had proved too unwieldy and costly.

Sally Jackson, a 41-year-old postal worker, expressed her regret that she’d jumped into the job market without an advanced degree and now had an insurance co-payment “too expensive to use.” Tom Furman, 47, had taken another path and earned an MBA — for which, he said with a rueful laugh, he still had $100,000 in debt to pay off.

“The insurance industry decided that they had to start whipping their profit horse ever since Hillary was tasked to reform this in 1993,” explained Larry Sillanpa, 67, the editor of the local Labor World newspaper. “To some extent, perhaps they’ve done that to discredit the Affordable Care Act.”

At the gathering, there was a pervading sense of distrust in Clinton — that, in the words of 22-year-old Kate Dayton, she would say anything. “She’s calling for breaking up the big banks, and her top five donors are big banks,” Dayton said.

If that distrust sinks in — and there are indications it already has — Minnesota will not be Clinton’s only problem state. But it’s also possible that her strong showing in Nevada, and her expected victory in South Carolina, will reverse that tide.

Last week, Clinton’s reinforcements gathered at a union office in Duluth to ramp up and fight back. Eight volunteers made the journey and got pep talks and call sheets. Zack Filipovich, 25, Duluth’s city council president, grabbed a phone and bemoaned how voters seemed to respond to concrete problems with fantastical hopes.

“At each level of government, it’s like a different mentality that people have,” Filipovich said. “In city government, there are things in people’s back yard — the streetlights, the garbage. When you move up the ladder to a big nationwide campaign, you sort of lose that tangibility. Free this, free that, free this — you start to lose the tangibility and think, ‘Oh, I want that!’ It’s a problem.”

Katie Humphrey, the staffer running the call session, flipped through a series of displays about how to talk to voters. Republicans could be struck from the list. It was not advised to argue things out with dedicated Sanders supporters. One volunteer expressed concern about a suggested line — something about how Minnesota’s race was going to be close. Was that really true?

“The polls have indicated that the race is very close,” Humphrey said. “We know the Sanders campaign is focusing on Minnesota.”