That is the highest turnout for a spring election since 2011 when the Supreme Court race came in the middle of massive protests against Gov. Scott Walker's collective bargaining restrictions and topped 34 percent.
Dallet defeated conservative Sauk County Circuit Judge Michael Screnock by an 11.5-percent margin, based on unofficial results. Dallet had nearly 56 percent of the vote compared with just over 44 percent for Screnock.
More than 995,000 voters out of nearly 4.7 million voting-age adults cast ballots.
Voters also rejected a constitutional amendment to do away with the state treasurer position. It was rejected by a 22 percent margin, with 61 percent voting against it and nearly 39 percent supporting.