REUTERS/Lucas Jackson
NBC and Fox News projected soon after polls closed that Sanders would defeat former Secretary of State Hillary Clinton in the Badger State.
Sanders has won six of the past seven states, but Clinton still holds a large delegate lead and remains the clear frontrunner for their party's nomination.
Sanders win somewhat expected. Entering the Wisconsin vote, Vermont senator held a nearly 3-point lead over Clinton in the RealClearPolitics average of recent polls.
Next up for the Democrats are the Wyoming caucuses, which will be held on Saturday. The next traditional primary state, New York, votes on April 19.