PROVO, Utah (AP) The Tanner Mangum show continued Saturday with another barely believable, come-from-behind victory for the 21-year-old freshman who returned from a Mormon mission in Chile just three months ago.

He threw a 35-yard touchdown to Mitchell Juergens with 45 seconds left to give BYU its second last-minute victory in as many weeks. The Cougars defeated No. 20 Boise State 35-24 as the Mangum magic continued.

BYU (2-0) trailed for most of the game. Mangum was far from perfect, completing 17 of 28 passes for 309 yards and throwing two interceptions. But the deep ball worked for him, and he came through when it mattered most.

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Mangum was making the first start of his career after another shocking victory last week. He introduced himself to the college football world after senior Taysom Hill was lost for the season with a lisfranc sprain in his foot.

Mangum played well in relief, but he snatched a place in BYU lore with a 42-yard Hail Mary touchdown pass to Mitch Mathews with no time remaining to beat traditional power Nebraska on the road.

Mangum struggled on intermediate passes much of the night, but the long ball was his friend. That and the fact he never lost confidence or got trigger shy.

''He said, `Sorry for making it so close,''' coach Bronco Mendenhall said.

Boise State quarterback Ryan Finley threw for 297 yards, one touchdown and three interceptions. Running back Jeremy McNichols finished with 95 total yards and two touchdowns for the Broncos (1-1).

The first half could be viewed in one of two ways: brilliant play by both defenses or a pair of sloppy offenses. The two teams combined for 10 punts and three interceptions in the first 30 minutes. BYU scored on its opening 75-yard drive then totaled a combined 87 yards on its next seven drives.

Boise State led by 10 going into the fourth quarter, but BYU scored 21 points unanswered.