About 24 hours.
The Sox had moved ahead of Kansas City on Friday night, when they made it 16 victories in 20 games.
"[Sunday's] game is a big one," White Sox manager Jerry Manuel said. "We can win the series. We're in position to do that."
Catcher Ramon Hernandez and relief pitcher Chad Bradford led the A's effort. Hernandez set his major-league high with five RBIs, two with a two-out first-inning double, two more with his 15th homer in the third and the last with a solo homer in the ninth.
Bradford stifled a Sox rally, struck out five and earned the victory with 2 1/3 innings of hitless relief.
The Sox threatened to make a game of it in the fifth inning when, trailing 6-0, they collected five hits, scored two runs and chased A's lefty starter Ted Lilly with the bases loaded and one out.
Bradford, a right-hander with a submarine delivery, replaced Lilly with Frank Thomas at bat and the big crowd on its feet screaming for a game-tying grand slam.
Bradford struck out Thomas and retired cleanup hitter Magglio Ordonez on a grounder to shortstop to stop the bleeding.
"I felt pretty good about our chances at least to close the gap at that time," Manuel said. "But Chad stopped us. They brought him in at the right time."
The A's bunched six runs and eight hits in the first three innings off Sox starter Jon Garland (8-8), who then settled down and blanked Oakland until he was replaced after five innings.
Garland wasn't responsible for all the A's scoring. First baseman Paul Konerko's error on a grounder by leadoff man Scott Hatteberg helped the A's to a 3-0 lead on three unearned runs off Garland in his 29-pitch first inning.
"We did not make that first play, and we put special emphasis on that," Manuel said. "After that, they hit a few grounders that got through ... and they hit some line drives."
The A's had three hits in the first, including a bunt single by Jose Guillen and Hernandez's two-run double that Carlos Lee momentarily lost in the sun in left.
"That's a tough left field to play in a 6 p.m. start," Manuel said. "I must say, though, that Carlos has played well for us in left."
Oakland improved its lead to 4-0 in the second. Mark Ellis walked to lead off the inning, took third on Hatteberg's one-out single and scored on Guillen's single that bounced over Joe Crede's head at third.
Some boos came from the standsand Dan Wright began warming up in the Sox bullpenin the third when Hernandez socked Garland with a two-run homer to make the score 6-0.
Successive doubles by Konerko and Crede produced the first Sox run. Catcher Jamie Burke, called up Friday from Triple-A Charlotte, singled home Crede for his first major-league RBI.
Then Bradford closed the door and the Sox were out of first.