USC's streaks of seven straight BCS bowls, 11-win seasons and top-four AP poll finishes? Those are all finished.

The Trojans' Pac-10 dominance over the past seven years? It's all but over after Stanford paved the way for a new West Coast champion.

Gerhart took time on the Coliseum field to savor the moment after rushing for 178 yards and three touchdowns in Stanford's (Not rated BCS, No. 25 AP) 55-21 victory Saturday over the Trojans (No. 9 BCS, No. 11 AP), who allowed the most points in school history.

"To do that against a storied program, a perennial power, it's the greatest feeling in the world," said the Pac-10 rushing leader, whose Heisman Trophy hopes are gaining momentum. "It was just will. The offensive line just moved people. We got after them and got downhill, and it was just a good offensive day."

How good? The loss was the Trojans' worst since a 51-0 defeat at home against Notre Dame in 1966. Coach Pete Carroll lost in November for the first time at USC after 28 straight victories. And for the second time in three weekends, Carroll endured the worst loss of his nine seasons.

"I'm not sure I have the right words to describe being humbled like this," Carroll said. "I don't really know where to put it. ... We have fallen apart and given our opponents the opportunity to do whatever they want, but you have to give Stanford a lot of credit."

Andrew Luck threw two touchdown passes and ran for another score for the Cardinal (7-3, 6-2 Pac-10), who followed up their surprising rout of Oregon last week with a strong start and a big finish at the Coliseum. The Trojans (7-3, 4-3) haven't lost to any other opponent at home since 2001, going 47-2.

Richard Sherman returned an interception 42 yards for a score with 11:41 to play, part of a 27-point fourth quarter for the Cardinal. After the postgame handshsake, the Cardinal raised their helmets and raced to their cheering section for their second celebration at the Coliseum in three years.

Stanford's 24-23 victory as a 41-point underdog in 2007 was a major shocker, yet this win barely even qualified as an upset. That might be the most incredible thing of all about the Trojans' downward slide, which will end with a minor bowl berth -- and with more than two losses -- for the first time since 2001.

"We came out there, and there was something wrong," USC safety Taylor Mays said. "It is very disappointing. It's almost sickening. To be a senior and leave a legacy like this, it's sickening."

Luck soundly outplayed fellow freshman quarterback Matt Barkley, while Gerhart steamrolled the once-vaunted USC defense. Stanford piled it on late, scoring four touchdowns in the fourth quarter after leading 28-21.

And the Cardinal did it on USC's homecoming, no less, in front of 90,071 somnolent fans.

"We were just consistent," Luck said. "Starting fast in both halves really helped us. Once we got rolling, we kept doing good things. "

Two weeks after USC's 47-20 loss at Oregon, the Trojans' defense was again embarrassed, giving up 469 yards.

Barkley went 21 of 31 for 196 yards with three interceptions in his third straight unimpressive game for the Trojans. Carroll has stuck with the freshman all season, but Barkley made turnovers on USC's first two drives to put the Trojans in an early 14-0 hole.

When Sherman jumped on Barkley's short pass and returned it down the USC sideline to put the Cardinal up 42-21, Coliseum fans headed for the exits with unfamiliar emotions.

"This isn't what we grew up watching," Barkley said. "I'm not used to this. ... I don't know what to think right now."

Joe McKnight rushed for 142 yards and a score for the Trojans, who fell behind 21-7 at halftime without top receiver Damian Williams, who has a sprained ankle. Brice Butler caught a scoring pass among his six catches for 96 yards, but USC's offense rarely found a rhythm after its first drive ended in a fumble by Barkley deep in Stanford territory.

Although USC kept it close through three quarters, the fourth was a long celebration for the Stanford band, a small cheering section and the players who already are bowl-eligible for the first time since 2001. After Gerhart's third touchdown, Stanford coach Jim Harbaugh even attempted a 2-point conversion, but USC stopped the try at the goal line.

Harbaugh's explanation for trying to pile on a couple more points: "I just honestly thought there was an opportunity coming off the ball, the way our backs were running and the way we were playing."

Said Carroll: "I don't know what they were thinking with that, but in that situation, they get to do whatever they want."

Few of the Cardinal's key players remain from their 2007 upset. Tavita Pritchard, the backup quarterback who led that 2007 victory, watched most of this game wearing a headset before playing the final minutes of the blowout.

The 2007 Cardinal couldn't even manage a winning season, but these Cardinal still have a shot at the Rose Bowl. Stanford finishes its Pac-10 season against California next weekend and would need some help to take the title.

"It's just an overwhelming feeling now," Luck said.