Watkins also had game-high totals of 13 rebounds and three steals for the balanced Broncos (6-0), who matched the school record for the best start to a season.
Backup point guard Mikey Thompson finished with 13 points, and Igor Hadziomeric added 12 points and seven rebounds. Forward Anthony Drmic finished with nine points, eight rebounds, while freshman Nick Duncan matched his career high of nine points.
Boise State (6-0) started the second half on a 15-5 run to create separation from a Portland State (5-1) team that was plagued by 15 turnovers. The Vikings turned the ball over nine times in the second half when the Broncos pulled away. Portland State only trailed 34-30 at halftime.
The Vikings, who made 46 percent of their shots in the opening half, struggled mightily from the field after halftime. The Vikings made only 21 percent of its shots in the second half to fall behind by as many as 26 points before a late run against the Boise State bench. The Broncos have led by 20 or more points in the second half of all six of their games this season.
The 76 points were a season-low total for Boise State, which entered the game as the top-scoring team in the nation with an average of 102 points per game. The Broncos also had their worst shooting performance of the season from 3-point range, making only 4 of 16 (25 percent). Coach Leon Rice's team entered the game shooting 46 percent from behind the arc while making an average of 9.8 3-pointers per game.
Boise State was nearly perfect from the foul line, making 22 of 25 attempts. Portland State made only 8-of-15 shots from the free-throw line.
Portland State was led by DaShaun Wiggins' 19 points. Tim Douglas had 12 points and Aaron Moore had 10 for the Vikings. It was Portland State's second loss to a Mountain West Conference team this season. The Vikings also lost at UNLV three weeks ago.