TUCSON, Ariz. — Mike Thomas broke the game open with a 52-yard punt return for a score, and Arizona whipped Arizona State 31-10 tonight, clinching the Wildcats' first winning season since 1998.

Nic Grigsby rushed for 114 yards and a touchdown and Willie Tuitama threw for 284 yards and two scores for Arizona (7-5, 5-4 Pac-10), which was expected to accept a bid to the Las Vegas Bowl.

Cardinal-clad Arizona students rushed the field to celebrate the Wildcats' most lopsided Territorial Cup triumph since a 30-6 victory in 1964. The Wildcats ended a three-game losing streak to the Sun Devils (5-7, 4-5), whose string of four straight bowl appearances ended.

Down 10-7 at halftime, the Wildcats blew the Sun Devils halfway to Casa Grande with 21 third-quarter points.

Arizona took a 14-10 lead on Tuitama's 18-yard pass to Delashaun Dean midway through the quarter.

Then cornerback Marquis Hundley picked off Rudy Carpenter's pass and returned it 47 yards to the ASU 34. Four plays later, Grigsby scored on a 12-yard run to make it 21-10.

Then came the backbreaker: the punt return by Thomas that electrified the Arizona Stadium crowd of 58,704.

Thomas fielded the bouncing ball over his shoulder, dodged a tackler and raced past a wall of blockers along the left sideline for his second punt return for a touchdown this season.

With that burst, the Wildcats effectively ended one of the more disappointing seasons in ASU history. The Sun Devils opened the season ranked 15th but matched a school record with six straight losses, and they went 1-6 against teams that entered with winning records.

Neither team looked like bowl material on a cloudy, 60-degree night in the desert. In the first eight minutes there was a fumble, an interception and seven penalties, including two personal fouls and an unsportsmanlike conduct on Arizona.

One of the personal fouls pushed the Wildcats back to their own 2 midway through the opening quarter. But the Wildcats marched 98 yards in 12 plays — their longest scoring drive of the season — to take a 7-0 lead on a 17-yard pass from Tuitama to Rob Gronkowski.

Arizona State cut Arizona's lead to 7-3 on a 40-yard field goal by Thomas Weber.

The Sun Devils used another Arizona miscue to take the lead midway through the second quarter. Arizona punter Keenyn Crier was ruled down when he put his right knee down while fielding a snap at his own 19, and five plays later Carpenter hit Andrew Pettes for a 2-yard touchdown pass to give the Sun Devils a 10-7 lead.

That was the high point for Carpenter, who completed 13-of-31 passes for 124 yards and a touchdown, and he threw an interception.

Carpenter started his 43rd straight game, the nation's longest active streak. He finished his career with 26 victories, tied with Dennis Sproul for second in school history.