ANKENY, Iowa — Across the room, sheets of paper taped to the wall reminded volunteers to organize with respect: “When you are tempted to make a statement,” one read, “ask a question.” Supporters gathered in the center of the room, waiting to knock on doors here in Ankeny, heard staffers speak of a welcoming movement. And Rep. Alexandria Ocasio-Cortez urged the crowd to stay “focused” on their own campaign — and be “happy” and “joyous” while doing it.

“Positivity is going to be what brings people into this movement,” the New York representative said.

Just eight days remain until the primary begins here in Iowa — and Sen. Bernie Sanders is leading the polls. For some Democrats, it’s a scenario they say they’ve dreaded and feared: waking up to the reality that the 78-year-old Vermont senator, an independent who has reshaped party policy and promised to bring a revolution to Washington, has a real shot at capturing the nomination. For the Sanders campaign, it’s been part rallying cry, part admonition: At events across Iowa this weekend, the candidate and his top surrogates repeatedly warned of a coming fight with forces that would try to stop them, at points celebrating the clash, at points cautioning supporters to stay positive.

With the series of polls showing Sanders at the top of the field in the first states — two more came out on Sunday alone, along with a national poll that has Sanders and Biden nearly tied — there is a feeling of palpable anticipation inside and around the campaign over what backlash, if any, might be coming.

“In these last eight days, things are gonna get crazy,” Ocasio-Cortez said on Sunday. “I don't even know what's gonna happen. And that's why we've gotta stay focused and committed as possible.”

“And let's make it joyous, y'all,” she said to cheers. “Let's make it joyous.”

Some rivals are already trying to capitalize on establishment anxiety. Pete Buttigieg asked supporters twice on Saturday to fend off Sanders by contributing to the mayor’s campaign.

“If things stay steady until the Iowa Caucuses in just nine days, Bernie Sanders could be the nominee of our party,” one fundraising email read.

And Amy Klobuchar is warning that having Sanders at the top of the ballot could hurt Democrats running in other races. "I don't come from a state as blue as Vermont," she said when asked about Sanders by reporters in Iowa.

“It looks like our opponents are pretty nervous that we’re going to win,” Sanders tweeted in response, along with an image of Buttigieg’s fundraising appeal. “Good! Let’s keep up the pressure.”

At a rally on Saturday night, a crowd of 1,400 people in Ames cheered Sanders on as he spoke of the concerns about his candidacy. “We are taking on the Democratic establishment, and all across the country, let me tell you that the big money interests are getting very nervous. They’re looking at recent polls in New Hampshire and in Iowa and they’re saying ‘Oh my god, Sanders can win,’” the senator said, feigning panic.

Michael Moore, the documentary filmmaker who joined Sanders and Ocasio-Cortez at seven campaign stops this weekend, told supporters, “The knives are out.”

He added, “The rich woke up this morning, and they read these articles and they're like, ‘Oh no, oh no, what are we going to do?’ So we'll see what they're going to do.”

A few days earlier, Moore told an audience that the Sanders campaign had been sending daily talking points to surrogates “admonishing us not to say one negative word about any of the other candidates.”

Moore, a voluble and aggressive surrogate on the campaign trail, arrived in Iowa prepared to rebut a range of potential attacks against the campaign. At his hotel on Sunday morning, he told crowds, he encountered a person who asked him why Sanders didn’t do more to help Hillary Clinton after she won the nomination in 2016.

“I said, ‘I’m glad you said that, because I happen to carry this with me,’” he said, brandishing two pieces of paper at the podium in a routine he has repeated from town halls to canvass launches.

On one sheet, he had written a list of 10 cities where he said Clinton held rallies for Barack Obama after she lost the nomination in 2008 — a gesture Moore praised at length. (Clinton held 46 events for Obama that year, according to a former Clinton campaign staffer who provided an accounting of her political events that year.) On the other sheet: a list of the 42 cities where Sanders held a rally for Clinton in 2016.

“If anybody says this to you,” Moore said of the claim that Sanders didn’t campaign for Clinton, “please point out how gracious she was to Barack Obama and how incredible — there are some days here when Bernie did four cities in one day for Hillary Clinton,” Moore said.

“These are the facts. I’ll post ’em on my site.”

In this campaign and his first presidential bid four years ago, critics have accused Sanders supporters of aggressive and insensitive online discourse. Earlier this month, Sen. Elizabeth Warren said she remembered Sanders telling her that he didn’t believe a woman could win the presidential election; in response, his supporters leaped to his defense online, calling her a liar and sending her a barrage of snake emojis on Twitter.

Sanders and his campaign staffers have urged his supporters to exercise respect and avoid any personal attacks. After one of his prominent supporters, former New York gubernatorial candidate Zephyr Teachout, wrote in an op-ed that Joe Biden had a “big corruption problem,” Sanders issued an apology and made a direct appeal to his followers.

“Please engage in civil discourse,” he said in a CBS News interview.

Sanders has still willingly feuded with Biden over policy, with his campaign continuing a days-long dispute over their social security records on Sunday night. “Joe Biden continues trying to hide his efforts to help Republicans cut Social Security,” Sanders' campaign manager, Faiz Shakir, said in a statement responding to the former vice president's comments that the Vermont senator has not been “consistent” on social security.

Here on Sunday, at the first of five stops with Sanders before he returns to Washington to participate in the ongoing impeachment trial, Ocasio-Cortez told volunteers that a positive campaign would welcome new voters.

“This should be about celebration,” Ocasio-Cortez said at the field office in Ankeny. “This is a celebration! We are establishing and reestablishing and reinvigorating our democracy here in this country. This is joyous. This is happy. That celebration of one another is what brings people in.”

The 11 candidates in the race have largely declined to attack Sanders directly.

The Buttigieg campaign’s email about Sanders didn’t come up at his town hall the next day in Des Moines. Asked by reporters if Democrats have underestimated Sanders, the former mayor said only, “It’s a terrible mistake to not take any candidate seriously.”

“This is the heat of competition,” said Buttigieg.