"That may have been a rush-the-floor-type moment for our fans," Marquette coach Steve Wojciechowski told reporters after the game.
The Golden Eagles have now won three of the past four meetings against their rivals. The Badgers won last season's game 77-61, but Marquette leads the series 44-38 dating back to 1949.
Friday's game in Milwaukee was a tight affair, with neither team ever leading by more than six points. There were 11 ties and 13 lead changes.
"Heck of a game from a college basketball fan perspective, back and forth, guys making plays at both ends," Wisconsin coach Greg Gard said. "But right down to the last play of not being able to secure a defensive rebound off a missed free throw, that cost us the game."
Marquette had a five-point lead with 5:39 left, but Wisconsin responded with a 6-0 run to take a one-point advantage with two minutes remaining. After a D.J. Carton basket to put Marquette up by two, Wisconsin called a timeout with 1:17 left, and the two teams proceeded to go back and forth trading baskets with zero stoppages in play for the next minute.
Wisconsin took a one-point lead with 5 seconds left on a D'Mitrik Trice jumper. Carton came back down and looked as though he was going to run out of time without getting a shot off, but he drew a blocking foul with 0.9 seconds left. He made the first free throw for the tie, then missed the second, but Lewis was able to tip in the offensive rebound as time expired.
"I wanted D.J. to make it. I wanted to go home. I wanted him to send us home," Lewis said. "But he missed it, I crashed in. In the beginning, during the previous free throws, some of the guys weren't crashing or boxing me out. So, I knew I'd have an opportunity to get a tip-in or something."
It was the perfect finish to cap off Lewis' breakout performance. The freshman from Baltimore had 18 points and eight rebounds, and he hit two 3-pointers and blocked two shots.
The Badgers are the fourth top-five team to lose in the season's first nine days -- with three of those losses coming to unranked teams. Virginia and Villanova lost last weekend, and Illinois fell to Baylor on Wednesday. A fifth top-five team will lose on Saturday, given that No. 1 Gonzaga will meet No. 2 Baylor in Indianapolis.
Marquette improves to 3-1, bouncing back from a loss to Oklahoma State, while Wisconsin suffered its first loss after opening the season with three consecutive victories.