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DUBUQUE, Iowa — Clara Wagner has been carefully considering the slate of 2020 Democratic candidates for months. By the time she walks into the mock caucus at Washington Middle School in Dubuque, Iowa, she has finally decided: She will be backing Sen. Amy Klobuchar of Minnesota.

“I like Amy Klobuchar because she thinks China is a national security threat, and also she wants interest rates for college to be lower,” says Wagner, standing in front of her eighth-grade social studies class in the school cafeteria, absentmindedly combing her fingers through her hair. “Also she wants to rejoin the Paris climate agreement, which I think is really great.”

All around the room, there are pictures of the 2020 candidates — Democrats, President Trump and his two Republican challengers — hanging high above the long lines of lunch tables and plastic stools. In less than a week, many of these students’ parents will head to the Iowa caucuses. Some will probably report to this exact cafeteria, an official precinct. Today, though, there are no swarming adults in campaign T-shirts, handing out buttons and preference cards. It’s just a group of 25 13- and 14-year-olds, free to throw their support behind whoever they think would make the best president.

When Katie Willey, Wagner’s teacher, first explained the rules of the caucus — how everyone picks a side, and then people try to persuade each other to change their minds — her students were immediately suspicious.

“Isn’t that kind of like peer pressure?” one of them asked.

In the cafeteria, that’s exactly how it plays out. When the students disperse to sit beneath their chosen candidates, Wagner heads straight to the picture of Klobuchar. Small groups of other students initially gravitate toward an assortment of different candidates — four to Sen. Bernie Sanders (I-Vt.), three to former vice president Joe Biden, a few to entrepreneur Andrew Yang and Sen. Elizabeth Warren (D-Mass.).

Eventually, though, almost all choose to leave their original posts, opting instead for a more populated table. The mock caucus begins to reflect the party breakdown of greater Dubuque, a formerly blue city that went for Trump in 2016: Roughly half the class ends up gathering under former South Bend, Ind., mayor Pete Buttigieg, a Democrat, the other half under Trump. One student is sitting by herself next to Warren.

It doesn’t look good for Klobuchar: Unless Wagner can persuade four of her classmates, she knows she’ll have to switch her candidate. For a candidate to be “viable,” or eligible for delegates, at an Iowa caucus location — or in her class — they need to win at least 15 percent of the vote. But all that persuading seems like a lot of work, Wagner says, and she doesn’t mind Buttigieg. So she crosses the cafeteria, smiles at the welcoming cheers from the Buttigieg table, and takes a seat.

Before now, most of Willey’s students didn’t know much about the Iowa caucuses. Many had no idea their state plays a special role as the first major contest of the election season. Mostly, they say, they just get annoyed by all the campaign ads on YouTube.

“Oh my God, that guy — Tom Steyer,” says Brooke Sullivan. “He is the absolute worst. He has like 79 different ads.” (Multiple students could recite lines from Steyer ads by heart.)

The mock caucus is something of a Dubuque tradition. Especially in an election year, many schools across the district hold some version of the event, says Mark Burns, the city’s executive director of secondary education. The ritual helps students understand their civic duty, he says: When they’re old enough to participate in the caucuses themselves, they’ll know what to do.

To help things run smoothly, Willey has enlisted the help of precinct officer Dianne Gibson, a local volunteer who has been overseeing caucus locations in Dubuque for years. Once everyone has settled on a candidate, Gibson tallies up the final numbers on a whiteboard.

“In a typical caucus, we would now have the realignment,” Gibson says. “Everyone who backed a non-viable candidate would pick their second choice. But here, the Warren person is the only one who can realign.”

The class turns to the back of the cafeteria, where Megan Dunlap is sitting quietly beside the picture of Warren. She’s wearing a lanyard covered with pictures of Deku from “My Hero Academia,” her favorite Japanese manga character. (“It’s the popular thing for nerds now,” she explains.)

Dunlap has a couple of options, Gibson says. She can pick a different candidate, or she can stay where she is, even though her vote then wouldn’t technically count.

“So what do you want to do?” Gibson asks Dunlap.

“I’ll stay here,” she says.

Dunlap doesn’t come from a family that cares much about politics. Her parents, she’s pretty sure, don’t even identify with a party. She didn’t know about the 2020 candidates until she spent the weekend researching them for this assignment. She liked what Warren had to say.

“I like that she is very LGBTQ pro. She supports equality of all races, sexualities and genders,” Dunlap says. “And I like the fact that she wants people to have free school so they can learn and get jobs that pay.”

In class, Dunlap doesn’t debate as much, or as well, as a lot of her other classmates, she says. She’s not sure why she felt so strongly about staying with Warren.

The final groups in the caucus break down mostly along gender lines: All but two of the students at the Trump table are boys, and all but two at the Buttigieg table are girls. That might be because a particularly popular guy went for Trump, and a popular girl went for Buttigieg, Wagner says.

“I feel like the boys, especially, just kind of follow each other,” she says. “None of them really express their opinion except one, and he’s super pro-Trump.”

The gender breakdown can make it even harder to go to the candidate you actually like, says Leah Chandlee, one of the two girls who ended up at the Trump table. Before school that morning, Chandlee says, she made sure that her friend, Leah Klapatauskas, was also planning to come out for Trump. It would have been scary to be the only girl at that table, Chandlee says.

Middle school is a perfect incubator for peer pressure: A bunch of kids thrown together in one building, still not too sure who they are or what they care about, worried about who in school likes them, and who doesn’t. As Lydia Denworth writes in the Atlantic, in middle school, “children are entering a period of maximum concern over acceptance or rejection and over how they will be perceived.”

It definitely affects the results of the caucus, Willey, their teacher says.

“I was really surprised how quickly some people changed. One girl started with Elizabeth Warren and then moved. She’s always been very pro-Warren — her parents are super political and they are caucusing for Warren. So I was like, ‘Hey, why’d you switch right away?’”

While middle-schoolers are definitely more susceptible to this kind of pressure, says Gibson, the precinct officer, it’s something she sees when she helps run real caucuses, too. After a while, people might look around and realize there aren’t many people in their group.

“Like the students today, they may think, ‘Why should I hold out? Maybe I’ll just go somewhere else right now. I won’t wait for the first realignment, I’ll just go. Because my second choice is viable.’”

But if caucus-goers switch their allegiance before the first count, Gibson says, their true preferences won’t be recorded. Even if a candidate isn’t “viable” in a certain precinct, she says, it’s still helpful to know exactly how much support they have across the state.

There are definitely problems with Iowa’s caucus system, says Nemmers, the student who switched from Biden to Buttigieg: Less confident people, with more shy personalities, will probably have a harder time expressing their true opinions. On the other hand, according to Chandlee, one of the Trump supporters, a caucus allows for open, thoughtful dialogue in a way a primary doesn’t.

“Maybe you open someone else’s eyes to something you see.”