Michelsen's third-quarter touchdown passes to Connor Kelley for 21 and 28 yards gave the Tigers the cushion they needed to post their fifth consecutive victory.
Michelsen completed 23 of 33 attempts for 281 yards and one interception. Kelley finished with career highs of 147 yards and 13 receptions.
Michelsen's 3-yard pass to Dre Nelson put Princeton (4-3, 3-1 Ivy) ahead for good at 10-7 in the second quarter. His 16-yarder to Scott Carpenter had Princeton up 17-7 before Robert Somborn's 5-yard touchdown pass 1:16 before the half cut the lead to 17-14 at the break.
Somborn was 23 of 40 for 315 yards for the Big Red (0-7, 0-4). Both of his scoring passes went to Lucas Shapiro, who had 12 catches and 165 yards, both career highs.