USC starter Paul Marchbanks (W, 7-2) took advantage of a liberal strike zone to get several LSU batters behind in the count early. In his 7 2/3 innings of work, he struck out five while allowing two earned runs.
Closer Blake Taylor pitched the remainder of the game and held the Tigers hitless for his tenth save of the season.
LSU starter Brian Wilson rebounded from a shaky start to essentially shut down the Gamecocks in the second half of the game, but the Tigers didn't provide enough offense to make his effort worthwhile.
USC scored all four of their runs against Wilson (L, 5-3), who lasted 5 2/3 innings and recorded eight strikeouts to go with nine hits.
The Tigers (26-14, 9-7 SEC) will try to take the series from the Gamecocks (30-9, 10-6) in Sunday's rubber game, scheduled for 12:30 p.m. CDT.
South Carolina took a 1-0 lead in their first at-bat when Trey Dyson used a two-out double to left center to score leadoff hitter Drew Meyer, who led off the inning with a nearly identical two-base hit.
The Gamecocks lead grew to 3-0 when Yaron Peters provided a two-run homer in the third inning. Despite allowing USC to put two runners with one out in the inning, Wilson rallied and got out of the inning. He went on to retire seven of the next eight batters he faced.
Meanwhile, the Tigers got their first run of the game with an RBI single from Jon Zeringue in the fifth inning.
But in the sixth, South Carolina got its lead back to three with an RBI single from Steve Thomas.
LSU finally got to Marchbanks in the eighth with a two-out rally. After Aaron Hill reached with a single, Wally Pontiff drove him in with double to right center. But the score stayed there when Taylor entered and struck out Barker to end the inning.
The Tigers went down loudly in their last at-bat, with Matt Heath flying out to deep right and Chris Phillips hitting a liner into the glove of USC third baseman Brian Buscher to end the game.