South Dakota State tied Omaha and IPFW for first place in the Summit League.
The Jackrabbits (17-5, 6-2) pulled away early in the second half with a 12-0 run to lead 55-43 and Omaha (14-8, 6-2) got no closer than eight the rest of the way.
Marshall scored 16 in the first half when South Dakota State led by as many as 13. The Mavericks had a 17-4 run spanning both halves to tie it at 43, but they missed their next eight field-goal attempts while the Jackrabbits rallied.
Deondre Parks scored 22 and Mike Daum 16 for South Dakota State.
Jake White had 18 points and Tim Smallwood had 15 for Omaha. Devin Patterson added 14 points, Tre'Shawn Thurman scored 13 and Tra-Deon Hollins 11.