Bernie Sanders is in the lead for the first time in an Iowa State University poll released Wednesday morning, reflecting other surveys indicating that the upstart 2016 candidate who came in a close second in the Iowa caucuses that year might well take the prize next week.

The poll has the senator from Vermont with 24% support among Democratic caucus-goers, followed by Sen. Elizabeth Warren of Massachusetts with 19%, former South Bend, Indiana, Mayor Pete Buttigieg with 17%, former Vice President Joe Biden with 15% and Sen. Amy Klobuchar of Minnesota with 11%.

The numbers are significant for both Buttigieg and Klobuchar, says Dave Peterson, an ISU political science professor who organized the poll, which was conducted with Civiqs. The former Indiana mayor dropped to third from first place in last month's ISU survey, putting him in a precarious position in a state where Buttigieg needs to do well to stay competitive for the nomination. Buttigieg lost a damaging one-third of his supporters from last month.

Sanders on the Trail View All 15 Images

Klobuchar – who has gone all-out in her neighboring state, even flying in for a quick rally in Council Bluffs last night after the Senate trial proceedings ended – has more than doubled her support from last month, coming close to the 15% viability threshold candidates need to be awarded delegates.

Sanders, Peterson says, is picking up support from candidates who have dropped out, such as former Housing and Urban Development secretary Julian Castro and Sen. Cory Booker of New Jersey. Castro has endorsed Warren and is campaigning for her here in Iowa and in other states.

The Vermont lawmaker's biggest asset is his unshakeable base.

"The stability of Sanders support is striking," Peterson said in a tweet analyzing the poll. "Once people say they support him, they are loyal." Sanders hadn't gained much until this month, Peterson said.

Iowa's caucuses, unlike primaries, are held at a specific time – 7 p.m. – and require voters to spend hours participating, That commitment means caucuses tend to draw out the more activist voters in each party, a factor analysts believe benefits someone like Sanders. The ISU poll also projected record turnout, with 80% of those surveyed planning to caucus.

The news suggests Sanders is solidifying a lead in the important first nominating contest. A poll by The Des Moines Register earlier this month also showed Sanders on top for the first time in that organization's surveys.

But there is still a fluidity to the race that could leave things up in the air after Monday's caucuses. Many voters at Democratic candidate events talk about their conflicted feelings in the choice – wanting to go with the person most aligned with their own views but worried about which candidate is best positioned to beat President Donald Trump.

Virginia Styron, 70, says she is determined to see a female president in her lifetime and is drawn to Warren and Klobuchar for that reason. Sanders, she says, "has good ideas, but I think is a bit too much for me," and she's still mulling Biden.

"Both of these women have the strength and knowledge to get things done, as well as Mr. Biden and all the others, but you have to pick one," Styron, an Iowa City resident, says.