Robby Mook, campaign manager for Hillary Clinton. (Victor J. Blue/Bloomberg News)

Just as they did in 2008, Nevada’s Democratic caucuses Saturday arrive at a critical time for Hillary Clinton, following her resounding defeat in New Hampshire. And once again, the state will be a testing ground for her campaign manager, Robby Mook, and the faith he has in his data-driven battle plan.

Eight years ago, it was Clinton’s humiliation in Iowa, not New Hampshire, that brought a gut-check moment to her struggling presidential campaign. The candidate and her husband huddled her high command at her Arlington, Va., headquarters to consider an urgent question: how hard to fight for Nevada?

Clinton’s defeat in Iowa had left the campaign unsure of its ability to win a caucus state against Barack Obama. There were good arguments that her time and dwindling resources might be better spent elsewhere.

Campaign chairman Terry McAuliffe suggested, “Why don’t we just get Robby on the phone here?” Some in the room had never even met their man in Nevada, Robby Mook, then barely 29 years old.

“He got on that call and said: ‘Here’s what we’re going to do. Let me tell you the metrics, and here’s how we’re going to win this thing,’ ” McAuliffe recalled. “The future of the campaign was on his shoulders — you talk about pressure.”

Once considered a firewall for Hillary Clinton, Nevada has sharply turned into a tight and unpredictable contest for the former secretary of state as Sen. Bernie Sanders steadily gains support from critical voting blocs. (Alice Li/The Washington Post)

Mook prevailed. Clinton carried the vote in Nevada, as her state director had promised she would, though Obama edged her out in delegates. Mook went on to run her winning operations in Ohio and Indiana.

Those victories were not enough to get the Democratic nomination, but Mook had earned his spurs in Clinton World. McAuliffe hired him to run his own successful campaign for governor of Virginia in 2013.

And when the former secretary of state decided to make another run at the White House, she tapped Mook as her manager for what they agreed would be a different kind of campaign, with a heavier emphasis on the kind of ground-level organizing that is Mook’s forte.

Nevada, where Democrats will caucus Saturday, and South Carolina, which holds its Democratic primary Feb. 27, were until recently considered Clinton’s “firewall” against what is turning out to be a stiff nomination challenge from Sen. Bernie Sanders (Vt.).

Lately, Clinton’s campaign has been working feverishly to lower expectations for how well she will do in Nevada. If she loses despite her built-in advantages with the state’s labor unions and Latino voters, it will be another blow to what’s left of her aura of invincibility.

No drama, lots of praise

Even in this difficult stretch, Mook is winning praise, both inside the campaign and among Clinton’s vast circle of second-guessers, for the airtight and drama-free campaign he has built.

Why minority voters matter for Democrats in Nevada and beyond

“He’s widely being viewed as the glue that is holding it together,” said one prominent Democrat, who spoke on the condition of anonymity to speculate about the state of the party front-runner’s campaign.

What glue cannot fix is the candidate herself and the fact that Clinton may be an ill fit for this angry, anti-establishment political moment.

“She has embraced a message of experience, but that by definition has her talking about herself and about the past,” said David Axelrod, who was Obama’s chief strategist in both of his presidential campaigns. Clinton, he added, needs to “bring down the rhapsodizing about all of her past achievements and find a way to frame it about the future.”

Aides and advisers to Clinton say they recognize the problem. As its next big personnel move, the campaign is expected to install a high-level communications adviser to travel with the candidate.

The culture of the Mook operation is a deliberate contrast from that of Clinton’s first presidential campaign.

In 2008, the campaign’s highly paid consultants stayed at Las Vegas’s lavish Bellagio hotel while Mook’s Nevada team was being outgunned on the ground by Obama’s campaign and scrounging to pay for office supplies.

Now, everyone lives under a tight budget; top campaign officials traveling to Iowa, for instance, were told to fly into Minneapolis or Moline, Ill., and drive, because the airline tickets were cheaper. Mook stays with supporters when he is on the road.

“I’ve certainly made it a priority on this campaign that we’re going to make investments where they matter,” Mook said in an interview the morning of the Iowa caucuses. “We’ve made big investments in people, in organizers, not only in hiring really good people but hiring them early enough that they could build really good relationships.”

Sanders got a later start, but he is catching up fast. In Nevada, he has spent twice as much as Clinton on television ads, according to the Las Vegas Review-Journal, and he has moved more than 100 paid staffers into the state.

Clinton’s team had sensed something similar going on in Iowa. In early January, the cash-flush Sanders campaign quietly doubled its number of organizers on the ground.

Mook refused to alter his own plan. “He put together an approach in April, and that approach we didn’t deviate from,” said Michael Halle, who played a senior role in the Iowa operation. “Of course, there were people in Iowa who were anxious. We talked about it. We talked about a lot of options. But I think had we hired 100 more staffers, it would not have made a difference.” Clinton squeaked by with the narrowest of wins.

Mook insisted that he, for one, has not been surprised by Sanders’s strength with the restive Democratic base.

“I have always believed there was at least 40 percent, but probably closer to 45 percent, of the Democratic primary electorate that is going to be, at best, open to another candidate and, at worst, insistent on drifting over to another candidate,” he said. “I tried to make that clear to the senior staff repeatedly.”

And as a Vermonter himself, Mook said, he has a special appreciation for Sanders’s political talent, as well as the perils of underestimating him.

“I literally grew up watching Bernie Sanders. I was a political junkie at a very young age, and I saw him,” Mook said.

In fact, Mook was all of 10 years old when he began sizing up his future nemesis. “It was that one congressional race in particular in 1990, where people just thought it wasn’t going to be possible for him to do this — that he could become the lefty mayor of Burlington, but there’s no way he would ever get into Congress,” Mook recalled. “And lo and behold, he did it.”

Looking to March

Now, the Clinton campaign is settling in for trench warfare. In a memo released as the polls were closing in New Hampshire, Mook argued for the long view, saying the real payoff to the campaign’s strategy would come in March.

“It’s important to understand why the campaign is investing so much time, energy and resources in states with primaries and caucuses in March,” he wrote. “The reason is simple: while important, the first four states represent just 4% of the delegates needed to secure the nomination; the 28 states that vote (or caucus) in March will award 56% of the delegates needed to win.”

One of Mook’s biggest challenges is managing the jitters of Clinton’s enormous circle of friends and supporters — and insulating the campaign from their influence.

“In politics, when you have a bad stretch, and she’s having one, you get a lot of advice from your friends, and she’s got a lot of friends,” Axelrod said.

So does her campaign manager, who has built a following of young operatives so loyal that they are known as the Mook Mafia. Preparing his team for a long haul, Mook has worked to keep up their morale and their sense of perspective about the ups and downs of a presidential campaign.

He dispatched 150 staffers from the campaign’s Brooklyn headquarters to work in New Hampshire in the final days before the primary. When they returned after Clinton’s defeat there, it was to cheers from their colleagues and an office festooned with balloons and thank-you posters in their honor. Mook got up and spoke of how proud he was of their efforts.

That, too, was a gesture reminiscent of his early days in Nevada. At a 2007 training session for his Silver State organizers, Mook handed out carabiners, the coupling links used by rock climbers to keep them safe if they fall.

Brad Komar, now Clinton’s Colorado director, still keeps his on his key chain, “and I know dozens of folks from that training session who still have it on them.”

It was a reminder not to lose faith in what they had built together. Or as Mook told them that day: “We’ll always be here to catch you.”