It’s all hands on deck in Iowa for Hillary Clinton in what is shaping up as the first big test for her 36-year-old campaign manager, Robby Mook, who vowed that he wouldn’t make the same mistakes that doomed Clinton in ’08. Yet on the eve of the caucuses, Clinton is struggling, her glow of inevitability as her party’s nominee challenged, and a potentially protracted fight looking more likely.

Mook has poured everything he knows how to do into Iowa. When he first came to Clinton’s notice, it was in Nevada in ’08, when she was ready to cede the state to Barack Obama, and he convinced her he could win it for her. He did, with 51 percent, though Obama got one more delegate than she did.

The sign on his campaign office wall back then said: “Set Goals, Experiment and Learn, Celebrate and Appreciate.” It encapsulates Mook’s millennial leadership style, and it’s a world apart from the 1992 motto of Bill Clinton’s campaign manager, James Carville: “It’s the economy stupid, and don’t forget health care.”

Obama field organizer Jeremy Bird, who first met Mook on Howard Dean’s campaign in 2003, says, “He’s incredibly unique in presidential politics in the sense that he is everything you could want in a campaign manager. He’s not in it for himself.” Mook doesn’t have a Facebook page and rarely tweets. “He isn’t interested in what you’re writing,” Bird added with a laugh, “and he’s always been that way.”

The son of a physics professor and a hospital administrator, Mook majored in the classics at Columbia University and still keeps a bookshelf with volumes in Greek. He was born in Vermont and grew up near the New Hampshire border. He is the first openly gay manager of a major presidential campaign, and his Iowa expertise is less about the state itself than applying lessons learned from multiple campaigns. As Howard Dean’s New Hampshire field director, he tried to pick up the pieces after the campaign’s gambit of sending hundreds of out-of-state volunteers to Iowa backfired.

Dean finished second to John Kerry in New Hampshire, but after he bowed out, Mook went to work for Kerry in the general and pulled out a narrow win for him in Wisconsin over George W. Bush. Mook loyalists describe his leadership style by saying that he puts the right people in place and “empowers” them. “He’s very meticulous in terms of their metrics,” says Bird, explaining how Mook sent staff to Iowa early to develop volunteer leaders from the community who are “metric-driven and accountable” and can deliver on caucus night. “A lot of leaders in campaigns are these authoritarian figures that have all the answers, and are louder than everybody else, that’s not Robby, he leads from behind,” says Bird.

Win or lose in Iowa, Mook has already accomplished something that’s always a central challenge in a large and high-pressure campaign—a culture that is remarkably free of the turf wars and infighting and leaks that hobbled Clinton in 2008. It did not go unnoticed in Hillaryland that after Clinton pal Terry McAuliffe won the governor’s race in Virginia in 2014, a winning campaign that Mook managed, there were no post-mortems about how Mook pulled it off.

For a metrics-driven guy, his friends say the Iowa results should be judged first by whether Clinton wins, but the margin counts. Did he keep it close? Did he exceed the 29 percent she got in ’08 when she finished third behind Obama and John Edwards? And most important, did he build a campaign to fight it out long-term? For now, everyone in Hillaryland is very protective of Mook. But if Clinton loses Iowa, he will feel the heat and the blame game will begin, perhaps not among the team he has built, but in the media for sure.

In a fundraising appeal that went out to supporters on Monday, Mook says this is “the most important week in the history of this campaign, and Hillary has never needed your help more…the polls show us in a real fight, and our opponent is outraising us—and using that money to outspend us on TV.”

That’s not just hyperbole, it’s true, and for Clinton it must seem like Groundhog Day. What’s different this time, though, is that Mook is ready for whatever the outcome. “When I talk to Robby, I’m very impressed how prepared he is for all contingencies. They haven’t gotten out there and beat their chest about what they’re doing, they’re just doing it,” says David Plouffe, who managed the Obama campaign in 2008 and saw how unprepared Clinton was to lose Iowa, and for a race quite different from the one she signed up for. Although she rebounded in New Hampshire, beating Obama by two percentage points, she really didn’t regain her footing until late in the primaries, when it was no longer possible to overtake Obama.

This time, Plouffe says Clinton can withstand whatever the result is in the first two states. If Sanders wins, her firewall in South Carolina will be tested, but it’s doubtful Sanders could overtake her with African Americans. The rest of the primary map is more favorable to her, as are the national polls, where she leads Sanders by double digits. “No one wins the presidency in a straight line,” says Plouffe. “History suggests there’s always a curve ball or two.”

Iowa is not only about winning, it’s about expectations, and Clinton has taken such a hammering that even a narrow win would be treated as a victory. Mook is doing everything he can to have a good outcome, and to keep everybody calm. It’s all hands on deck this last week with Planned Parenthood, labor unions, and the Human Rights Campaign all in Iowa rallying for Clinton. Can they reach the young voters flocking to Sanders? Mook will soon find out.