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LOS ANGELES -- The Los Angeles Dodgers are a happy bunch, but they're not celebrating just yet.

They hope to be doing so Thursday.

Manny Ramirez and Nomar Garciaparra homered, and the surging Dodgers beat the San Diego Padres 12-4 Wednesday night to clinch a tie for their first NL West championship in four years.

The Dodgers' victory combined with Arizona's 4-2 loss at St. Louis gave Los Angeles a four-game lead over the Diamondbacks with four games remaining.

The Dodgers can clinch their fifth postseason berth since 1988 on Thursday afternoon if the Diamondbacks lose at St. Louis, or Thursday night when they face the Padres in their final home game of the regular season.

"Whichever way it happens, as long as it happens," first-year Dodgers manager Joe Torre said. "If we get a chance to celebrate, we'll do it. We still have a little work to do. Tonight we couldn't have asked for anything better. It's been a bumpy road, no question. The players have handled what they've had to handle."

The Dodgers have won just one postseason game since winning the World Series 20 years ago.

Jake Peavy, 12-1 with a 2.21 ERA in 21 career starts against the Dodgers, will pitch the series finale for the Padres against Greg Maddux, a winner of 354 games in his career.

Peavy was originally scheduled to pitch last Friday, but was pushed back twice because his third son was born premature. Manager Bud Black said everything seems fine with the baby now.

"Peavy played some catch yesterday and he's ready to go," Black said. "He was away from the team and away from the field for four days, away from baseball activity."

Ramirez, Garciaparra, James Loney and Angel Berroa drove in two runs each for the Dodgers, who have won 18 of their last 23 games to move a season-high eight games over .500. They were 65-70 and trailed the Diamondbacks by 4½ games before beginning their turnaround Aug. 30 in Arizona.

"It feels great," Ramirez said. "We still have to come and get the win and we are going against one of the best pitchers in the league. We just have to come back and battle and play hard."

Ramirez said he wasn't thinking about the postseason when the Boston Red Sox traded him to the Dodgers on July 31.

"I was trying to fit in, play the game and show people that I could play and play hard," he said. "That was my attitude."

Rookie Clayton Kershaw (5-5) earned the victory, allowing six hits and three runs in 5 2/3 innings. The 20-year-old left-hander walked two and struck out seven before being relieved by Chan Ho Park with two outs, a runner at second and the Dodgers leading 4-3 in the sixth. Park retired Nick Hundley on a fly to center to end the inning.

"This is the best I've felt maybe all year," Kershaw said. "When I first got up here, I was rushing some things. I felt really comfortable on the mound tonight. It's an awesome feeling to be where I am right now."

The Dodgers broke a 2-2 tie against rookie Mike Ekstrom (0-1) in the fifth on an RBI double by Garciaparra and Berroa's squeeze bunt.

Chase Headley's two-out RBI double in the sixth drew the Padres within one run and chased Kershaw, but Ramirez hit a 3-1 pitch from Cla Meredith into the left-center field pavilion for a two-run homer in the bottom of the inning to make it 6-3. Ramirez is hitting .398 with 17 homers and 53 RBIs in 50 games with the Dodgers.

San Diego's Brian Giles hit a sacrifice fly off Joe Beimel in the seventh, making it 6-4.

The Dodgers made it a rout in the eighth, scoring six runs off Clay Hensley and Dirk Hayhurst on RBI singles by Andre Ethier, Matt Kemp and Berroa, a two-run double by Loney and a run-scoring double by Chin-lung Hu.

"Everybody is contributing right now," Garciaparra said. "For us to be in the position we are in and doing what we are doing right now, with putting that many runs up, everybody is doing their job. That's what we have to do if we are going to reach our ultimate goal, which is getting to the playoffs."

The Padres took a 2-0 lead in the fourth on back-to-back doubles by Giles and Adrian Gonzalez and a two-out, RBI single by Hundley. The Dodgers tied it in their half and chased starter Shawn Estes, scoring on Garciaparra's leadoff homer and a two-out, RBI single by Kemp. After Kemp's hit, Estes walked Russell Martin to load the bases for his third walk of the inning before Ekstrom retired Ramirez on a grounder to second.

Estes allowed six hits and two runs in 3 2/3 innings while walking three and striking out two.

Game notes

Dodgers 2B Jeff Kent singled as a pinch hitter in the seventh, his first action since he injured his left knee Aug. 29. SS Rafael Furcal struck out as a pinch hitter in the eighth in his first appearance since he went on the disabled list May 6 because of back problems. ... Giles' fourth-inning double was the 400th of his career, and he scored twice, giving him 1,101 runs scored. ... The Dodgers have a 29-21 record since Ramirez joined the team, and are 16-5 in September -- best in the majors. The Kansas City Royals rank second with a 16-7 mark. ... Kemp struck out against Meredith in the sixth for his 149th strikeout of the season, tying the franchise record set by Bill Grabarkewitz in 1970. ... Former four-time world champion Shane Mosley threw out the ceremonial first pitch. Mosley will face Ricardo Mayorga on Saturday night at The Home Depot Center in nearby Carson, Calif., in a 12-round junior middleweight bout.