PULLMAN, Wash. (AP) _ Idaho put itself in control of the Big West Conference race with a 31-3 victory over Utah State on Saturday before 23,429, the biggest crowd in school history.

Idaho remained unbeaten in the Big West, improving to 5-2 and 3-0 in conference play. Meanwhile, Utah State fell to 2-5, 0-2 in the Big West.

The Vandals defense gave up only 171 yards, led by tackle Mao Tosi. Tosi had two sacks and intercepted Jeff Crosbie's pass in the fourth quarter.

Idaho quarterback Greg Robertson tossed touchdowns to three receivers as he completed 14 of 31 passes for 215 yards. Chris Lacey served as Robertson's favorite target, hauling in five catches for 55 yards, including a 12-yard touchdown putting Idaho up 14-0 with 1:01 to go in the first half.

Utah State's only score came on Brad Bohn's 44-yard field goal with :03 to go before halftime. The Aggies had numerous dropped balls and committed 15 penalties.

Idaho's defense harassed Crosbie the entire night. Crosbie was just 9-of-28 for 97 yards and was sacked eight times.

The Vandals used an effective mix of running and passing as they controlled the ball for just over 35 minutes, with 51 runs for 112 yards. Junior Anthony Tenner scored Idaho's third touchdown, scampering 6 yards for a 21-3 lead early in the third quarter.

Idaho, with its record crowd, has met the NCAA quota of averaging at least 17,000 fans per game. The Vandals have been leasing Washington State's Martin Stadium in order to meet NCAA attendance requirements.