IOWA CITY, Iowa — Bernie Sanders's campaign has been telling its aides that it expects to win the Iowa caucuses, setting expectations high in the final days leading up to the Feb. 3 contest.

Although the Vermont senator has largely remained in Washington to sit for President Trump's impeachment trial during the last few weeks, his organizers and campaign staff on the ground in the state remain confident that Sanders's message has won enough Iowa Democrats over to secure a crucial victory.

During a campaign organizer meeting for staff members and volunteers attended by the Washington Examiner last Friday, leadership explained they no longer believe they need to reach undecided voters. Instead, volunteers were expected to examine data collected by the campaign to target existing supporters and ensure they show up on the day of the caucus.

"I get in trouble when I say this, but I'm confident in a win here in Iowa," said Sanders's Iowa co-chairman Stacey Walker in the meeting.

That Sanders's campaign believes it has the necessary core support for victory stands in contrast to his rivals, such as former South Bend, Indiana, Mayor Pete Buttigieg, 38, who have been aggressively campaigning across the state attempting to court undecided voters. In contrast to Sanders, 78, Buttigieg believes the record-high number of undecideds in the state could swing to him on caucus day.

Similarly, former Vice President Joe Biden, 77, is trying to expand his base of support. Because his team recognizes it suffers from a weak turnout operation, which it says is because it started the campaign relatively late in the primary season, winning over new voters is necessary to avoid an embarrassing finish of fourth place or worse.

[ Read more: Democrats concerned Bernie Sanders could nab 2020 nomination but lose to Trump]

Both candidates have scheduled a blitz of campaign stops, many of which will be in small towns scattered through rural Iowa, in an attempt to win over independents and even Republicans. Many of those events are town halls, where Buttigieg and Biden will try making last-minute pitches to undecided voters.

Meanwhile, Sanders and his surrogates are relying on large rallies to maintain enthusiasm among supporters. In college towns such as Iowa City and Sioux City, Sanders has called on left-wing filmmaker Michael Moore, celebrity Democratic New York Rep. Alexandria Ocasio-Cortez, and rock bands such as Portugal. The Man to keep young Democrats engaged. Those rallies have brought in thousands of attendees, often five times or larger than those attracted by Biden or Buttigieg.

Supporters of Sanders feel bolstered by recent polls that show him pulling ahead of his rivals. Three of the last four reputable surveys in the state show him in first place. A report from Emerson College, released Monday, showed Sanders with a 9-point lead over Biden — his best showing in the state so far.

"I think he's got momentum. He's really starting to lead here. He's just been talking about the really positive and great things he's accomplished, and it's working," said Bert Miller, 63, who says he's been a supporter of Sanders for 40 years. "There's no use in changing anything now."

The Sanders campaign has long said that its strategy depends on winning each primary contest as it comes, rather than focus on the national numbers — where Biden still remains ahead. That fact has only served to motivate Sanders's supporters further.

"It's kinda between him, Buttigieg, and Biden now. He's in a good competitive spot," said Thomas Jones, who is only 17 but will be able to caucus for Sanders because of the state's voting rules. "The numbers are pretty clear at this point, and eventually, the rest of the party will fall in line. But he needs to win here, and I think a lot of people know that."

Although few in Iowa believe Sanders is capable of replicating his 2016 performance — when he narrowly lost to former Secretary of State Hillary Clinton by a quarter of a percentage point at 49.59% — the nature of the caucus system makes it likely that Sanders will outperform his current polling. RealClearPolitics currently has Sanders averaging at 25% support. A surge of five more points on caucus day, his supporters say, could ensure a win.

"I am feeling good about Iowa, and I'm feeling good about other states. You can tell how good I feel, by how nervous the establishment is getting," Sanders said in Sioux City on Sunday, one of the few events he was able to attend amid impeachment proceedings in Washington. "Suddenly, Donald Trump is talking about our campaign."