Harris got 20 of his points in the first half for the Spartans (18-1, 7-0 Big Ten), who completed a season's series sweep of the Hoosiers.
Branden Dawson tacked on 13 points and nine rebounds.
Travis Trice and Denzel Valentine had 10 points each for MSU.
The Hoosiers (12-7, 2-4) were paced by Yogi Ferrell with 19 points.
Noah Vonleh notched a double-double of 13 and 13 rebounds.
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