USC opened the second half with a 19-12 run, overcoming a three-point halftime deficit and building a 46-42 lead with 12:23 left. The Trojans led 50-43 with 9:40 to play, but the Golden Bears (10-5, 2-1), using a smaller, quicker lineup, battled back.
"The key to the thing I thought was (when) Nikola Knezevic went in the game," Cal coach Mike Montgomery said. "Lewis was a guy that was really hurting us, and Nik pretty much took him out. Once Nikola went in and kind of changed our defensive focus, all of a sudden our team changed."
Cal went on a 7-0 run, pulling into a 50-50 tie on Randle's floater in the key with 7:35 remaining. Robertson hit a 3 from the left wing during the Bears' surge.
Randle hit a pair of free throws, putting Cal up 53-51. Robertson hit two more from the line then Randle rebounded his own miss and scored, making it 57-51 Cal with 4:37 to play. Jamal Boykin hit a 12-foot jumper from the right corner, giving Cal a 59-51 lead, its largest of the game to that point.
"We were up seven, but on the road there isn't a lot of room for error," USC guard Mike Gerrity said. "You've really got to take advantage of each possession and down the stretch we made some mistakes mentally, and (we) really just lost control at the end."
Cal ended the game with a 24-9 run, and Knezevic held Lewis to just four points over the final 9:54 as the Bears took control.
"We knew coming into the game whoever was going to be the most physical team was going to win the game," Knezevic said. "In the second half, that was us."
Saturday's game shaped up as a battle of contrasting styles. USC entered the game with the nation's No. 1 scoring defense, limiting opponents to 54.5 points per game.
Cal, meanwhile, came in averaging 80 points per game, second best in the Pac-10.
The Bears led by as many as seven points in the first half but were never able to shake the Trojans.
Cal built a slim 30-27 halftime lead, but the game was played at the Trojans' grind-it-out pace. USC forced 10 Cal turnovers in the first half, four of those by Randle.
Still Randle scored 11 points in the first on 4-of-6 shooting.
Lewis, coming off a 22-point night against Stanford, had 12 points at halftime.
Cal started running later in the second half and finished with 12 fast break points compared to zero for USC.
"The game really turned around when we got the tempo going our way," Robertson said. "It's really tough to not play their game when they're making shots. When they're making shots they're able to get back and get their half-court defense set.
"We were able to turn that around in the second half. Nikola came in and kind of got them out of rhythm a little bit, and we were able to do some of the things that we're more accustomed to."
Guard Jorge Gutierrez, one of Cal's key reserves, missed his second straight game since spraining his right knee against Stanford. USC reserve guard Donte Smith, who sprained an ankle against Stanford and was questionable for Saturday's game, played.