SANTA CLARA, Calif. -- USC, the football school that once ruled its conference with an iron hand, is finally back on top after an eight-year absence, thanks in large part of a goal-line stand.

When the Trojans won the Pac-10 title in 2008, it was the seventh consecutive year they finished with at least a share of the conference championship.

USC had not won a conference title since then until the No. 10 Trojans defeated Stanford for the second time this season, beating the No. 12 Cardinal 31-28 in the Pac-12 championship game Friday night at Levi's Stadium.

USC (11-2) figures to move up in the final College Football Playoff rankings, which will be announced Sunday at noon. But there is little chance the Trojans will advance to the top four and land a berth in the national championship playoff.

The Trojans are expected to play in one of the New Year's Six bowls, probably the Fiesta Bowl, while Stanford (9-4) could wind up in a number of bowl games, with the Holiday Bowl being the most likely destination.

USC beat Stanford 42-24 back on Sept. 9., but this one was a lot more difficult. And it was a fourth-quarter goal-line stand that turned out to be the pivotal play.

Trailing 24-21 with 8:00 left, Stanford faced a fourth down at the USC 1. Coach David Shaw eschewed a tying field goal and went for the touchdown.

"No hesitation at all," Shaw said.

Bryce Love, who finished with 125 yards rushing, was not in the game on that fourth-down play, but Cameron Scarlett has been the Cardinal's goal-line back all season. This time, however, Scarlett was stopped short of the goal line by Uchenna Nwoso and Jordan Iosefa.

"You're talking about the one of the best short-yardage teams in the nation, and we made the stop -- unbelievable," USC coach Clay Helton said.

But it left the Trojans in an offensive hole.

"We've been so good in that situation, it was a no-brainer to go," Shaw said. "Even if we don't get it, we've got them at the 1-yard line."

But USC quarterback Sam Darnold, who finished 17 of 24 for 325 yards, two touchdowns and no interceptions, threw a 54-yard completion to Michael Pittman Jr. on a second-and-9 play from the 2-yard line to get out of trouble.

"I was about to pull it down and run, then I saw Michael break open," Darnold said.

The Trojans parlayed it into a 99-yard drive that ended with Ronald Jones II's 8-yard scoring run, which gave USC a 31-21 lead with 4:22 left.

Helton thought the goal-line stand and the 54-yard pass were the biggest plays of USC's season.

"No question," he said. "It was time to dig deep. Those are the plays that define you. Go 99 yards to finish the game; that defines this team.

"This is the best finishing bunch I've been associated with in my 23 years."

Stanford quarterback K.J. Costello, who ended up 10 of 22 for 192 yards, two touchdowns and no interceptions, threw a 28-yard scoring pass to Kaden Smith to make it 31-28 with 2:09 left, but the Cardinal's ensuing onside kick attempt went out of bounds.

"To be down two scores, looks like it's over to fight back, make it a tight game, have a chance, says a lot about this team," Shaw said.

Jones rushed for 140 yards for the Trojans, who never trailed in the game.

USC scored the game's first points on a 7-yard touchdown pass to Pittman, and the Trojans controlled much of the first half. But a 1-yard touchdown run by Scarlett with 34 seconds left in the half reduced USC's lead to 17-14 at the intermission.

NOTES: When USC beat Stanford 42-24 in Los Angeles on Sept. 9, the Trojans outgained the Cardinal 623-342. This time USC outgained the Cardinal 501-343 ... USC QB Sam Darnold is projected to be the No. 1 overall pick in the 2018 NFL Draft by NFLDraftScout.com. ... Stanford RB Bryce Love has 1,973 rushing yards this season, second best in Stanford history and 46 yards shy of Christian McCaffrey's school-record 2,019 yards, achieved in 2015. Love had 52-yard run in the third quarter Friday, giving him 12 runs of 50 yards or more this season, the most in FBS in 10 years. ... The Pac-12 North had been 6-0 in conference championship games before USC's win.