Carroll, Iowa (CNN) With just a couple of tables, a stack of boxes and some Bernie Sanders posters tacked to the wall filling their one big, empty room, there's no doubt: This crew looks like the underdogs.

Three volunteers -- all getting involved in a political campaign for the first time -- and a young staffer named Charlie Dominick are trying to harness the momentum of a surprise, last-minute surge a few days after Sanders had come to town.

"You can definitely tell -- people are getting excited. People that didn't want to volunteer before are ready to start now," said Emma Schmidt, 21, of rural Calhoun County who administers three pro-Sanders Facebook pages and hosts speech and debate watch parties -- but has never caucused before.

In Iowa, it actually does all come down to turnout. A larger turnout should favor Sanders, who is banking on bringing younger voters who haven't participated before in presidential elections to the caucuses. Smaller turnout will likely favor Hillary Clinton, who has concentrated on the more traditional, committed Democratic audience. How those two campaigns are able to get their backers to show up Monday will play the key role in determining how far the Democratic primary goes

In 2004, about 124,000 people showed up -- with that year's liberal insurgent, Howard Dean, particularly let down by the turnout, losing to John Kerry and never recovering. Four years later, in 2008, an intense three-way race and Barack Obama's vaunted field operation nearly doubled that number, to 239,000 participants.

No one -- not even Sanders himself -- is forecasting turnout that high again.

"Frankly, I don't think we can" match 2008, he said Monday.

But Sanders' overwhelming advantage in polls among young people and first-time caucus-goers makes clear that the more people who participate, the better he'll do.

Clinton's campaign, however, is way ahead of the organization game.

Her hyper-organized campaign manager Robby Mook dispatched 30 paid staffers to Iowa last spring while Sanders was still little more than a protest candidate. By August, Clinton's campaign had at least one supporter in each of Iowa's 1,681 precincts.

The jump-start in recruiting an army of volunteers and "precinct captains" meant Clinton's campaign could more quickly identify her supporters, make personal contacts, deliver door-hangers and help her backers find their caucus sites. That's all particularly important in Iowa, where caucusing can be a three-hour, public affair that pits friends and neighbors against each other.

"It takes a lot of time and energy to get these people really engaged," said Norm Sterzenbach, a strategist at GPS Impact and former Iowa Democratic Party executive director. "You need local volunteers to help you do this. You need Iowans to help explain this strategy and get people to do this."

At Clinton's office

Just three blocks east from Sanders' office here in Western Iowa, Clinton's storefront shop is humming. A dozen volunteers, including two coordinators, and local organizer Kate Magill are there. The walls are decorated with schedules, pro-Clinton talking points and posters signed by Clinton's famous surrogates. Tina Ward-Pugh, a 16-year member of Louisville, Kentucky's council, is back in Iowa to "finish what we started eight years ago."

They're part of a Clinton operation that has already finished two January test runs of their caucus-day plans and their get-out-the-vote operation, which will unleash thousands of volunteers departing from more than 150 locations.

Photos: Hillary Clinton's life in the spotlight Photos: Hillary Clinton's life in the spotlight Hillary Clinton accepts the Democratic Party's nomination for president at the Democratic National Convention in Philadelphia on July 28, 2016. The former first lady, U.S. senator and secretary of state was the first woman to lead the presidential ticket of a major political party. Hide Caption 1 of 43 Photos: Hillary Clinton's life in the spotlight Before marrying Bill Clinton, she was Hillary Rodham. Here she attends Wellesley College in Massachusetts. Her commencement speech at Wellesley's graduation ceremony in 1969 attracted national attention. After graduating, she attended Yale Law School. Hide Caption 2 of 43 Photos: Hillary Clinton's life in the spotlight Rodham was a lawyer on the House Judiciary Committee, whose work led to impeachment charges against President Richard Nixon in 1974. Hide Caption 3 of 43 Photos: Hillary Clinton's life in the spotlight In 1975, Rodham married Bill Clinton, whom she met at Yale Law School. He became the governor of Arkansas in 1978. In 1980, the couple had a daughter, Chelsea. Hide Caption 4 of 43 Photos: Hillary Clinton's life in the spotlight Arkansas' first lady, now using the name Hillary Rodham Clinton, wears her inaugural ball gown in 1985. Hide Caption 5 of 43 Photos: Hillary Clinton's life in the spotlight The Clintons celebrate Bill's inauguration in Little Rock, Arkansas, in 1991. He was governor from 1983 to 1992, when he was elected President. Hide Caption 6 of 43 Photos: Hillary Clinton's life in the spotlight Bill Clinton comforts his wife on the set of "60 Minutes" after a stage light broke loose from the ceiling and knocked her down in January 1992. Hide Caption 7 of 43 Photos: Hillary Clinton's life in the spotlight In June 1992, Clinton uses a sewing machine designed to eliminate back and wrist strain. She had just given a speech at a convention of the International Ladies' Garment Workers Union. Hide Caption 8 of 43 Photos: Hillary Clinton's life in the spotlight During the 1992 presidential campaign, Clinton jokes with her husband's running mate, Al Gore, and Gore's wife, Tipper, aboard a campaign bus. Hide Caption 9 of 43 Photos: Hillary Clinton's life in the spotlight Clinton accompanies her husband as he takes the oath of office in January 1993. Hide Caption 10 of 43 Photos: Hillary Clinton's life in the spotlight The Clintons share a laugh on Capitol Hill in 1993. Hide Caption 11 of 43 Photos: Hillary Clinton's life in the spotlight Clinton unveils the renovated Blue Room of the White House in 1995. Hide Caption 12 of 43 Photos: Hillary Clinton's life in the spotlight Clinton waves to the media in January 1996 as she arrives for an appearance before a grand jury in Washington. The first lady was subpoenaed to testify as a witness in the investigation of the Whitewater land deal in Arkansas. The Clintons' business investment was investigated, but ultimately they were cleared of any wrongdoing. Hide Caption 13 of 43 Photos: Hillary Clinton's life in the spotlight The Clintons hug as Bill is sworn in for a second term as President. Hide Caption 14 of 43 Photos: Hillary Clinton's life in the spotlight The first lady holds up a Grammy Award, which she won for her audiobook "It Takes a Village" in 1997. Hide Caption 15 of 43 Photos: Hillary Clinton's life in the spotlight The Clintons dance on a beach in the U.S. Virgin Islands in January 1998. Later that month, Bill Clinton was accused of having a sexual relationship with former White House intern Monica Lewinsky. Hide Caption 16 of 43 Photos: Hillary Clinton's life in the spotlight Clinton looks on as her husband discusses the Monica Lewinsky scandal in the Roosevelt Room of the White House on January 26, 1998. Clinton declared, "I did not have sexual relations with that woman." In August of that year, Clinton testified before a grand jury and admitted to having "inappropriate intimate contact" with Lewinsky, but he said it did not constitute sexual relations because they had not had intercourse. He was impeached in December on charges of perjury and obstruction of justice. Hide Caption 17 of 43 Photos: Hillary Clinton's life in the spotlight The first family walks with their dog, Buddy, as they leave the White House for a vacation in August 1998. Hide Caption 18 of 43 Photos: Hillary Clinton's life in the spotlight President Clinton makes a statement at the White House in December 1998, thanking members of Congress who voted against his impeachment. The Senate trial ended with an acquittal in February 1999. Hide Caption 19 of 43 Photos: Hillary Clinton's life in the spotlight Clinton announces in February 2000 that she will seek the U.S. Senate seat in New York. She was elected later that year. Hide Caption 20 of 43 Photos: Hillary Clinton's life in the spotlight Clinton makes her first appearance on the Senate Environment and Natural Resources Committee. Hide Caption 21 of 43 Photos: Hillary Clinton's life in the spotlight Sen. Clinton comforts Maren Sarkarat, a woman who lost her husband in the September 11 terrorist attacks, during a ground-zero memorial in October 2001. Hide Caption 22 of 43 Photos: Hillary Clinton's life in the spotlight Clinton holds up her book "Living History" before a signing in Auburn Hills, Michigan, in 2003. Hide Caption 23 of 43 Photos: Hillary Clinton's life in the spotlight Clinton and another presidential hopeful, U.S. Sen. Barack Obama, applaud at the start of a Democratic debate in 2007. Hide Caption 24 of 43 Photos: Hillary Clinton's life in the spotlight Obama and Clinton talk on the plane on their way to a rally in Unity, New Hampshire, in June 2008. She had recently ended her presidential campaign and endorsed Obama. Hide Caption 25 of 43 Photos: Hillary Clinton's life in the spotlight Obama is flanked by Clinton and Vice President-elect Joe Biden at a news conference in Chicago in December 2008. He had designated Clinton to be his secretary of state. Hide Caption 26 of 43 Photos: Hillary Clinton's life in the spotlight Clinton, as secretary of state, greets Russian Prime Minister Vladimir Putin during a meeting just outside Moscow in March 2010. Hide Caption 27 of 43 Photos: Hillary Clinton's life in the spotlight The Clintons pose on the day of Chelsea's wedding to Marc Mezvinsky in July 2010. Hide Caption 28 of 43 Photos: Hillary Clinton's life in the spotlight In this photo provided by the White House, Obama, Clinton, Biden and other members of the national security team receive an update on the mission against Osama bin Laden in May 2011. Hide Caption 29 of 43 Photos: Hillary Clinton's life in the spotlight Clinton checks her Blackberry inside a military plane after leaving Malta in October 2011. In 2015, The New York Times reported that Clinton exclusively used a personal email account during her time as secretary of state. The account, fed through its own server, raises security and preservation concerns. Clinton later said she used a private domain out of "convenience," but admits in retrospect "it would have been better" to use multiple emails. Hide Caption 30 of 43 Photos: Hillary Clinton's life in the spotlight Clinton arrives for a group photo before a forum with the Gulf Cooperation Council in March 2012. The forum was held in Riyadh, Saudi Arabia. Hide Caption 31 of 43 Photos: Hillary Clinton's life in the spotlight Obama and Clinton bow during the transfer-of-remains ceremony marking the return of four Americans, including U.S. Ambassador Christopher Stevens, who were killed in Benghazi, Libya, in September 2012. Hide Caption 32 of 43 Photos: Hillary Clinton's life in the spotlight Clinton ducks after a woman threw a shoe at her while she was delivering remarks at a recycling trade conference in Las Vegas in 2014. Hide Caption 33 of 43 Photos: Hillary Clinton's life in the spotlight Clinton, now running for President again, performs with Jimmy Fallon during a "Tonight Show" skit in September 2015. Hide Caption 34 of 43 Photos: Hillary Clinton's life in the spotlight Clinton testifies about the Benghazi attack during a House committee meeting in October 2015. "I would imagine I have thought more about what happened than all of you put together," she said during the 11-hour hearing. "I have lost more sleep than all of you put together. I have been wracking my brain about what more could have been done or should have been done." Months earlier, Clinton had acknowledged a "systemic breakdown" as cited by an Accountability Review Board, and she said that her department was taking additional steps to increase security at U.S. diplomatic facilities. Hide Caption 35 of 43 Photos: Hillary Clinton's life in the spotlight U.S. Sen. Bernie Sanders shares a lighthearted moment with Clinton during a Democratic presidential debate in October 2015. It came after Sanders gave his take on the Clinton email scandal. "The American people are sick and tired of hearing about the damn emails," Sanders said. "Enough of the emails. Let's talk about the real issues facing the United States of America." Hide Caption 36 of 43 Photos: Hillary Clinton's life in the spotlight Clinton is reflected in a teleprompter during a campaign rally in Alexandria, Virginia, in October 2015. Hide Caption 37 of 43 Photos: Hillary Clinton's life in the spotlight Clinton walks on her stage with her family after winning the New York primary in April. Hide Caption 38 of 43 Photos: Hillary Clinton's life in the spotlight After Clinton became the Democratic Party's presumptive nominee, this photo was posted to her official Twitter account. "To every little girl who dreams big: Yes, you can be anything you want -- even president," Clinton said. "Tonight is for you." Hide Caption 39 of 43 Photos: Hillary Clinton's life in the spotlight Obama hugs Clinton after he gave a speech at the Democratic National Convention in Philadelphia. The president said Clinton was ready to be commander in chief. "For four years, I had a front-row seat to her intelligence, her judgment and her discipline," he said, referring to her stint as his secretary of state. Hide Caption 40 of 43 Photos: Hillary Clinton's life in the spotlight Clinton arrives at a 9/11 commemoration ceremony in New York on September 11. Clinton, who was diagnosed with pneumonia two days before, left early after feeling ill. A video appeared to show her stumble as Secret Service agents helped her into a van. Hide Caption 41 of 43 Photos: Hillary Clinton's life in the spotlight Clinton addresses a campaign rally in Cleveland on November 6, two days before Election Day. She went on to lose Ohio -- and the election -- to her Republican opponent, Donald Trump. Hide Caption 42 of 43 Photos: Hillary Clinton's life in the spotlight After conceding the presidency to Trump in a phone call earlier, Clinton addresses supporters and campaign workers in New York on Wednesday, November 9. Her defeat marked a stunning end to a campaign that appeared poised to make her the first woman elected US president. Hide Caption 43 of 43

Most of them watched Clinton lose eight years ago, and they say her organization now matches the Barack Obama operation that beat her in 2008. Still, there's a sense of anxiety over whether Sanders can pull in voters who aren't even on their radar.

Jean Guy, a 65-year-old Catholic high school teacher in town, said it's hard to dispute Sanders has "caught fire."

"Who would disagree with anything Bernie says?" she said. "I mean, great -- I want all that, too. And I would also, while we're at it, like two weeks guaranteed at Disney World every year."

For the final days before Monday night's caucuses, they'll mostly drop their attempts to find potential caucus-goers and persuade them. Instead, they will enter full get-out-the-caucus mode -- dispatching herds of volunteers to knock on doors, deliver door-hangers and find ways to drive people to their local precincts if they can't drive themselves.

Sanders playing catch-up

Sanders has drastically expanded his Iowa operation in December and January as his poll numbers -- and online donations -- surged.

He's nearly matched Clinton now on the ground. She has 26 organizational offices with paid staffers throughout Iowa; he has 23 -- even if they're hastily opened and sparsely decorated.

"The Sanders campaign was really still building the plane as they were flying it, but to their credit they have built an impressive organization given the time they had to build it," said Brad Anderson, a Democratic strategist who led President Barack Obama's re-election effort in Iowa in 2012.

Tom Clark, a 60-year-old county maintenance worker in Maple River, had never considered volunteering for a politician until he heard Sanders on a local radio show.

"I was one of these guys that maybe just let it go, didn't care," he said. "I said, 'God, nobody's talking about this my whole life, and this guy's talking about it.' It inspired me."

Sanders' campaign got a late start in harnessing the thousands of people who show up at his events. Now, though, his camp carries iPads and asks attendees to register electronically.

It allows them to skip the data entry and quickly follow up with people -- especially potential first-time caucus-goers -- who only show up in the campaign's final days.

Sanders himself offered a blunt assessment of his Iowa operation after a meeting with steelworkers in Des Moines on Monday.

"We started out organizing in Iowa a lot later than Senator Clinton did. She was here in 2008; has the experience we didn't have. She's done this before, we didn't. She has a very strong organization. And I applaud her for that," he said.

"But I will tell you that the last couple of months we have gained a whole lot of ground and again I think we stand a real chance to create a large voter turnout."

The makeup of his support -- young and new to the process -- means his challenge is doubly difficult: Not only has Sanders had to race to build a competitive field organization in two months; his organizers and volunteers must try to reach a much larger universe of potential supporters than Clinton's operation is targeting.

"On the Sanders campaign, they're obviously focused on turning out their supporters, but I'm pretty confident they're also banking on a wave of new, additional supporters -- engaged, watching, wanting to participate, but not on their radar screen," Anderson said.

O'Malley fans' second choice

One major unknown that has Iowa Democrats buzzing is the race's third candidate: former Maryland Gov. Martin O'Malley.

Under Democratic caucus rules, candidates have to reach 15% support in a precinct to be considered "viable" and eligible to win any delegates. Supporters of candidates who fall short, though, get the choice to realign behind another contender.

O'Malley's support is small, but those who are backing him tend to be committed caucus-goers who understand the process, would never skip it and know how to cut deals.

If the race is a nail-biter, they could make a difference -- particularly in precincts with odd numbers of delegates at play -- 11, rather than 10, for example -- because they could tip what looks like a tie into a victory for either Clinton or Sanders.

O'Malley backers say they're hearing from both campaigns -- each cribbing Obama's 2008 strategy of trying to become the second choice of voters who started in the camps of the lowest-polling candidates. Several Democratic strategists said they expect O'Malley's supporters to split about 60/40 in Sanders' favor.

Location, location, location

The campaigns are telegraphing their strategies to turn out votes through where the candidates themselves are spending time.

Each of Iowa's 1,681 precincts has delegates to win -- and the caucus results are based on who nets the most delegates, not who gets the most overall supporters.

Clinton's events have been concentrated in delegate-rich urban and suburban areas -- particularly those she lost in 2008. Winning those areas, or even keeping them close so Sanders can't run up a big lead, could be the difference.

Sanders, meanwhile, has hit college towns and typically unvisited portions of Iowa's cities -- but he has also spent more time in rural areas where Clinton could fare well. Keeping her from running up an insurmountable lead in those areas could give him a win.

Iowa strategists said Clinton's schedule has been particularly shrewd, while Sanders' reflects a candidate intent on broadening his appeal.

"I think it makes a ton of sense to go to those areas where you need turnout to really be high and clearly the schedule reflects that on the Clinton side," Anderson said.

"He really has been focused on the college towns, which seems to be a strategic move. ... But getting college students to caucus is a really, really heavy lift."