The Gamecocks (16-14) will play 14th-ranked Tennessee, the East Division's top seed, in the quarterfinals Friday after winning their first-round game for the second time in the last three years.
Mississippi State (15-15) had not lost an opening game since the tournament last was in Nashville, in 2001. But the Bulldogs, the Western Division's winningest team in this tournament since 1999 and the fourth-seed, finished the season failing to win consecutive games against SEC opponents.
South Carolina, the No. 5 seed from the East, beat the Bulldogs 83-61 on Feb. 11 in the teams' only other meeting, and a team that had 10 SEC games decided by six points or less got to enjoy a rare easy victory by taking advantage of Mississippi State's own mistakes.
The Bulldogs, starting three freshmen, outrebounded South Carolina 34-27. But they turned the ball over 17 times, and the Gamecocks turned those into 22 points.
Mississippi State started strong enough, hitting its first four shots and leading 9-2 within the first three minutes.
But South Carolina settled down after missing 10 of its first 13 shots by hitting 10 of the next 19. The Gamecocks also started pressuring the young Bulldogs and scored 13 points off seven turnovers before Kinsey scored to give South Carolina its first lead at 15-13 with 9:14 left.
The Gamecocks led as much as 31-20 on a basket by Dwayne Day with 2:03 to go off another turnover, and they led 32-25 at halftime. Mississippi State last got within double digits on a bucket by Wesley Morgan at 46-38 with 8:19 to go before South Carolina scored the next six points to put the game away.