In the poll, conducted and released by Marquette Law School on Friday, 29 percent of Democratic primary voters said Sanders was their first choice and former New York Mayor Michael Bloomberg came in second with 17 percent of support, Presstv Reported.
Vice President Joe Biden ranked third with 15 percent while former South Bend, Indiana, Mayor Pete Buttigieg and Senator Amy Klobuchar (D-Minn.) garnered 13 and 11 percent of votes respectively.
Biden has seen his support in the midwestern state drop significantly from the poll's first iteration in November when he had a comfortable lead over the 78-year-old Vermont senator with 30 percent to 17.
The Friday poll was carried out among 1000 registered voters interviewed by cell phone or landline in Wisconsin between February 19 and 23, with a margin of error of 3.6 percentage points.
Of those surveyed, 56 percent said they still might change their mind before the state's April 7 primary.
Sanders won Wisconsin in the 2016 presidential elections, easily defeating Hillary Clinton by 13 points.
The state is a key battleground in the 2020 election race. President Donald Trump narrowly won the state by just over 20,000 votes in 2016. It was the first time the state had voted for the Republican nominee since 1984.
With Sanders winning New Hampshire and Nevada over the past weeks, he is in the driver's seat against his seven rivals as the race turns toward South Carolina and then Super Tuesday.