LOS ANGELES -- No. 13 USC rallied from a two-touchdown halftime deficit Saturday to defeat Utah 28-27 in the Los Angeles Memorial Coliseum.

The Trojans (6-1, 4-1 Pac-12) trailed the Utes (4-2, 1-2) 21-7 at intermission, the result of three first-half fumbles.

Quarterback Sam Darnold threw two of his three touchdown passes, running back Ronald Jones II scored on a front-flip into the end zone to give USC the lead, and defensive back Ajene Harris stopped Utah quarterback Troy Williams on a game-deciding two-point conversion attempt with an open-field tackle to preserve the win.

"I've got confidence in my tackling, so I took the best angle possible and locked up," Harris said. "Our defense's whole mindset was to get a stop, so I felt confident we were going to get a stop."

Utah could have played for overtime with an extra-point kick, particularly after lining up for the two-point conversion and forcing USC to exhaust its final timeout.

On the heels of the success the Utes had that final drive, however, Utah coaches and players alike believed they could get back into the end zone.

"As an offense, we loved the call. We just weren't able to execute how we wanted," Utah running back Zack Moss said. "You want to see your coach have that much faith in you with so much at stake."

Utah head coach Kyle Whittingham's faith was unshaken, despite the misfire.

"Bottom line, we came one play short," he said. "I thought it was the right decision. Defense played 80 snaps and had major problems stopping them in the second half. Darnold was on fire."

USC's ability to sustain drives played a critical role in the Trojans' second-half rally, wearing down the Utah defense over the course of the final 30 minutes.

Jones' touchdown run that gave USC the lead capped an 11-play, 93-yard drive that included a mix of key pass completions and long rushes.

The USC defense, which gave up several explosive plays in the first half, buckled down for much of the second half. Linebacker Cameron Smith set the pace with 16 tackles and an interception.

"They went to zone (defense in the second half) and it kind of slowed us down," Williams said. "But it really came down to one play to win the game."

The outcome does not come to that one play if the USC defense does not bow up for much of the second half, according to Trojans safety Chris Hawkins.

"We found our rhythm," he said. "The offense started scoring, which gave the defense more confidence. When we have our full confidence, it's hard to stop us."

Utah's only score of the second half was a big one. After Williams found a wide-open Siale Fakailoatonga for a 37-yard gain on a fourth-and-1, Williams rushed for a 1-yard touchdown. Williams finished the game with three touchdowns: one passing, one rushing and one receiving.

USC began its rally in the third quarter when Darnold found tight end Tyler Petite in a narrow window for his second touchdown reception of the evening. Tight end Josh Falo, who made his first career catch and score on Oct. 7 vs. Oregon State, tied the game on a 1-yard touchdown reception.

Darnold finished 27 of 50 passing for 358 yards. Jones rushed 17 times for 111 yards. Williams finished 16 of 27 for 262 yards for Utah.

Utah capitalized on three USC turnovers and Williams threw one touchdown pass and caught one as the Utes led 21-7 at halftime.

Williams' 33-yard pass to Demari Simpkins capped a nine-play, 79-yard Utah drive that began when USC's own promising drive ended on a dropped backward pass from Darnold to Jones.

Before that, the USC defense had not surrendered a touchdown off a turnover this season despite the Trojans committing 13 heading into the game -- tied for 13th most in FBS.

Although the USC defense had not previously surrendered a touchdown off a turnover, Utah was able to reach the end zone on another fumble in the first half Saturday. Utah defensive back Marquise Blair scooped a Darnold drop forced by linebacker Kavika Luafatasaga and returned it 18 yards for a touchdown.

The fumble was Darnold's second of the first half. USC's opening drive ended at the Utah 34-yard line on a botched handoff exchange with Jones.

Utah's offense moved the ball effectively early with explosive plays, but a missed field-goal attempt and Smith's interception of Williams snuffed two Utes scoring opportunities.

Utah scored its first offensive points when Williams caught a 5-yard pass from Simpkins. USC scored its only points of the first half when Darnold found tight end Petite on a seam route up the middle. With no Utah safety back, Petite went untouched 52 yards to the end zone.

Darnold finished the half 14 of 25 for 213 yards. Four USC drives stalled on Utah's side of the field.

NOTES: The win extended USC's home winning streak to 14 games. The streak, which began in Clay Helton's first game as head coach in October 2015, came against Utah. ... USC RB Ronald Jones II has scored at least one touchdown in each of the last 13 games he has played, a nation's-best streak tied with Penn State RB Saquon Barkley. ... Utah QB Troy Williams' touchdown reception was his first career catch. ... USC LB Cameron Smith's first-half interception marked the fourth of his career, all four of which have come against Utah. Smith made three interceptions in the Trojans' 2015 win over the Utes. ... Attendance was 72,382.