A political scientist based in Iowa said Monday that 2020 hopefuls Sen. Elizabeth Warren Elizabeth WarrenWarren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon No new taxes for the ultra rich — fix bad tax policy instead MORE (D-Mass.) and former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq A socially and environmentally just way to fight climate change MORE boast the strongest ground campaigns out of the crowded Democratic field ahead of state’s first-in-the-nation caucuses.

“The consensus is among people I talk to that the Warren campaign is very, very strong on the ground, that the Buttigieg campaign is close to just as strong in the sense that they have a very large number of organizers, a lot of offices, massive numbers of volunteers,” Dave Redlawsk, a visiting professor at the University of Iowa, told Hill.TV.

“But the more important thing is that they’re actually out there identifying voters and tracking them and reaching out to them — probably most effective [of] the entire group,” he added.

Redlawsk added that while Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.) boasts a strong presence in the Hawkeye State, his campaign has been relying a lot on past support he gained during his previous presidential bid in 2016.

“The Sanders folks figured that they’ve got many of those people locked,” he said. “But I don’t think they’re quite as intensely active as the Warren and Buttigieg campaign.”

The Vermont independent led a critical Des Moines Register/CNN poll of Iowa voters released last Friday.

The survey, which is widely considered the most authoritative in Iowa, showed Sanders with 20 percent support among likely Democratic caucus-goers, followed by Warren at 17 percent, Buttigieg at 16 percent and former Vice President Joe Biden Joe BidenCast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response Biden tells CNN town hall that he has benefited from white privilege MORE at 15 percent.

All four contenders are poised to take the stage at Tuesday’s debate in Iowa, which will be the last time the candidates will debate before the the Feb. 3 caucuses.

—Tess Bonn