The victory extended the Badgers' win streak -- the longest in the nation -- to 14. Wisconsin, now 5-0 overall and 2-0 in the Big Ten, totaled 461 yards of offense against the Spartans, who slipped to 4-1 overall and 0-1 in the conference.
P.J. Hill, who finished with 155 yards on 34 carries, scored first on a five-yard run. But Michigan State's Jehuu Caulcrick scored twice from two yards out.
Tyler Donovan hit Travis Beckum for a 2-yard TD and Kyle Jefferson for a 65-yard score that gave the Badgers a 21-14 lead. Michigan State responded with Devin Thomas' 80-yard TD reception.
Mehlhaff then hit field goals of 35 and 47 yards to make it 27-21 Wisconsin.
MSU managed a third-quarter field goal but David Gilreath scored from one yard out to make it 34-24. Mark Dell caught a 3-yard TDs and another MSU field goal tied it at 34-34 -- setting the stage for Mehlhaff's final field goal heroics.
Michigan State’s Javon Ringer tallied 145 rushing yards and 88 receiving yards.