STANFORD, Calif. -- The suppositions of September have given way to an unexpected reality in October in the Pac-12.

Washington State ended an eight-game losing streak to Stanford and turned the Pac-12 race upside down by upsetting the 15th-ranked Cardinal 42-16 on Saturday night at Stanford Stadium.

The Cardinal were the preseason favorites to repeat as Pac-12 champion and won their first three games. Washington State dropped its first two contests, including a season-opening loss to Eastern Washington, an FCS school.

But Stanford (3-2, 2-2 Pac-12) was clobbered for the second straight game, losing to Washington 44-6 last week and getting dominated by the Cougars.

Meanwhile, Washington State (3-2, 2-0), which beat Oregon 51-33 last week, joins Washington as the only two teams unbeaten in Pac-12 play. In a matter of eight days, the Cougars have dominated the two teams that have won every Pac-12 title since 2008.

"For us these past two weeks have really been important," Washington State wide receiver Gabe Marks said. "We've become the team we thought we could be. It took a couple games to figure it out."

Coach Mike Leach said the early losses required the coaches and players to re-examine everything.

"There's a point where everybody has to be brutally honest," Leach said. "We had to focus and everybody had to just do his job."

Cardinal running back Christian McCaffrey, who was limited to 49 rushing yards against Washington last week, had 35 rushing yards on eight carries and one reception for 5 yards against the Cougars. He had one carry in the second half and that came early in the third quarter. He did not play in the fourth quarter.

Cardinal coach David Shaw said McCaffrey was simply beat up, and saw no reason to expose him to more punishment.

"We'll see how he is during the course of the week," Shaw said.

Washington State had 458 yards of total offense compared with 296 for Stanford. The only touchdown the Stanford offense scored came on the final play of the game. The Cardinal's defense scored Stanford's other touchdown.

"We did not play well," Shaw said, "and for every positive, we had a negative, and that's not the sign of a good football team. It's not the sign of a Stanford football team. Now, I understand what's going to be said for the next 48 hours. That's fine. I can take it."

Washington State quarterback Luke Falk was 30 for 41 for 357 yards, four touchdowns and two interceptions. River Cracraft had seven receptions for 130 yards and a touchdown.

"He's a talented, very polished quarterback," said Stanford defensive back Dallas Lloyd, who had an interception. "He managed the game well and had good reads.

"But we feel we have so much potential and we're just not living up to it."

Cardinal starting quarterback Ryan Burns went 19 of 25 for 222 yards, one interception and a touchdown pass. After being sacked eight times last week, Stanford quarterbacks were sacked four times Saturday.

The Cardinal lost consecutive games for only the second time under Shaw, in his sixth season as Stanford's coach, and have lost games in consecutive weeks for the first time with Shaw at the helm.

Washington State increased a 14-3 halftime lead to 21-3 by marching 81 yards after receiving the second-half kickoff. Running back James Williams scored the touchdown on a 2-yard run.

"I thought the most important series for us was the first series of the second half," Leach said.

The Cardinal got back in the game when Falk's pass was intercepted by cornerback Frank Buncom, who returned it 26 yards for a touchdown to reduce the Cougars' lead to 21-10. But Washington State increased the margin to 28-10 on Falk's 17-yard pass to Marks later in the third quarter. Falk added 16-yard scoring pass to Cracraft to make it 35-10.

Quarterback Keller Chryst played one series for Stanford in the first half and played briefly in the second, completing 2 of 9 passes for the game. Shaw did not comment on any possible quarterback change.

NOTES: Cardinal S Justin Reid was penalized for targeting and ejected from the game for a hit on Washington State QB Luke Falk in the third quarter. Falk sat out one play. ... Stanford played without starting CBs Alijah Holder (shoulder) and Quenton Meeks (undisclosed), WR Francis Owusu (concussion), FB Daniel Marx (undisclosed), and OT Casey Tucker (undisclosed). ... Washington State K Erik Powell was 0 for 4 on field-goal attempts this season before Saturday's game, and he missed a 43-yard field-goal try on the final play of last season's 30-28 loss to Stanford. He missed a 35-yard field-goal attempt in the first half Saturday to make him 0 of 5 for the season and didn't get a try in the second half.