What follows is the latest installment of a Fortune series looking at the the most influential women on Clinton’s 2016 team. When this series wraps, we’ll turn our attention to the most powerful women on the GOP side of the race.

Brynne Craig, 30, Deputy National Political Director

By the time Brynne Craig started her career, the Rolodex was as much of a relic as those pink “while you were out” message slips. But if Craig, 30, did have an old-style Rolodex sitting on her desk, it would be fat—bulging with names of Democratic foot soldiers all over the country, from phone bank volunteers to precinct captains.

Craig does field operations. She’s done that job for presidential candidate Hillary Clinton in 2008, for the Democratic Congressional Campaign Committee—charged with electing House members—in 2012, and for victorious Virginia gubernatorial candidate Terry McAuliffe in 2013. She also picked up some useful organizing skills working for Democratic nominee Barack Obama after Clinton dropped out in 2008, but the former First Lady is clearly her first political love.

Craig’s adoration of Hillary Clinton dates back to her Arizona childhood, when her music-industry father was rooting for Bill Clinton’s 1992 victory, voraciously reading newspapers and sharing his opinions with his 8-year-old daughter. “That was the first time I was really aware of politics,” she recalls. “We would talk a lot about [the campaign].” Her Republican mother, however, had different ideas: “George [H.W.] Bush was her guy.”

Craig liked Bill Clinton, but she really liked his wife. “When I was little, I thought if Hillary ever ran for President I wanted to work for her,” she recalls. That moment finally came in 2007, after she graduated from Smith College and joined her campaign in Nevada. It turned to be a high-wire act: With Obama’s win in Iowa, and Clinton’s dramatic comeback in New Hampshire, the early Nevada caucus—considered a bellwether for western states—was billed as a tie-breaker.

Like Iowa, Nevada runs a caucus rather than a primary, and in 2008 this in-person process was a strange new system to state voters, unlike in Iowa. So a lot of what Craig did was education–Caucus-101 meetings and simulations of caucus days. She oversaw 43 precincts. On election day, Clinton was the top-vote getter (though a complicated process gave Obama more delegates)—making Nevada the only caucus state to fall into her 2008 column during that grueling primary battle.

After Clinton conceded and dropped out, Craig was off to the swing state of Ohio for the general election, where Obama would beat GOP nominee John McCain—and show off an awe-inspiring grass roots operation. “We built a neighborhood team model all across Ohio, voters talking to their neighbors and friends, block by block,” Craig recalls. “The lady who was the cashier in the grocery store was the one knocking on your door.”

Craig took away from that experience a lesson that holds true even in an age of social media and online communication. “We used to say people will come to a campaign because they believe in the candidates,” says Craig. “But the reason they stay is the relationships we have. I still talk to my precinct captains. Social media engages people, but you have to take that second step of going off line and continuing the relationship.”

That will come in handy in her current job as part of the “Mook Mafia” —named for her mentor, Clinton campaign manager Robby Mook—where she will need to secure endorsements from local and state officials and keep the campaign’s relations with grass-roots groups warm and fuzzy, even when times get tough.