Harris had a career-high 26 points -- with 17 coming in the first half -- to lead the Spartans to a 73-56 win against Indiana in Bloomington.
The sophomore hit 5 of 10 3-point attempts and 5 of 6 free-throw attempts. He also had five steals and four rebounds.
Starting out 9-9 early, Harris hit a 3-pointer, converted a 3-point play and hit another 3-pointer to break the game open for the Spartans.
Indiana made another run to pull within 25-25, but a Branden Dawson layup and a pair of Harris 3's extended the lead to 33-24 going into halftime.
Keith Appling chipped in 14 points, all in the second half after getting in early foul trouble.
Dawson had 13 points on 6 of 7 shooting -- 5 of 5 in the first half.
Point guard Yogi Ferrell led Indiana with 17 points.
The Spartans host No. 3 Ohio State on Tuesday at Breslin Center.