The Bulldogs (23-4, 16-0) tied the school record for consecutive wins set in 1999-2000 and matched the best start in Horizon League conference play set by Wisconsin-Green Bay in 1995-96. They also swept the season series from the Vikings (13-13, 9-5), who had beaten them in the conference tournament championship game last season.
Howard had 21 points and 13 rebounds; Hayward 19 points and 11 rebounds as they outrebounded the Vikings by themselves, 24-20.
D'Aundray Brown scored 14 points for Cleveland State, which had a six-game winning streak snapped and lost for the first time in 15 conference home games.
The Vikings were outrebounded 46-20 and finished 1 of 15 from beyond the 3-point arc.
Cleveland State, which hadn't lost a home game to a league opponent since falling 50-48 to Butler on Dec. 4, 2008, took an early lead before getting into foul trouble.
The Vikings led 16-10 before going 8 minutes without a field goal. Shelvin Mack scored four points for Butler in a 12-3 run for a 22-19 lead, but the Bulldogs couldn't pull away as they kept turning the ball over.
On Thursday night, they had 11 turnovers before halftime, then came back to win 68-57 at Youngstown State.
Butler had nine turnovers in the first half against the Vikings — but a Cleveland State defensive lapse enabled the Bulldogs to take a 29-27 halftime lead. After Norris Cole converted a three-point play to tie it with 3.9 seconds left, the Vikings allowed Hayward to dribble the length of the court and lay the ball in at the buzzer.
The Bulldogs opened the second half with an 8-2 run. The Vikings' Aaron Pogue picked up his fourth foul with 15:11 left and guard Brown got his fourth 56 seconds later. Butler soon opened a 10-point lead and maintained it.
The Bulldogs' win matched a 15-game streak by Siena that was snapped by Niagara on Friday night.