Harvey hit a 3 with 2:20 left and the Eagles led 82-73. Mike Scott answered with a 3-pointer on the other end and, after Brandon hit two free throws, Connor Hill made a 3 to cut Idaho's deficit to 84-79 with 1:31 remaining.
Brandon again made a pair of free throws, but another trey from Scott pulled the Vandals within four with 66 seconds to play.
Idaho (7-7, 2-1) got a stop before two free throws by Wiggs made it 86-84.
Harvey and Ty Egbert traded two free throws apiece and the Eagles led 88-86 with 14 seconds to go.
After Bogdan Bliznyuk made 1 of 2 from the stripe, Scott missed a 3 at the buzzer.