Ryan Craig also scored for the Southeast Division-leading Lightning, who have won 15 of 19. Tampa Bay took the shootout 2-1 and is 11-3 in games that have been decided after regulation.
The Lightning will face the second-place Thrashers in Atlanta on Thursday. Although both have 71 points, Tampa Bay is ahead of the Thrashers because the Lightning have played one fewer game.
Nathan Horton scored twice for the Panthers, 1-12 in games decided in overtime or a shootout.
St. Louis got Tampa Bay even at 2 with his 36th goal of the season, scored during a power play with 12:17 left in the third.
Horton scored on his second breakaway of the game to put the Panthers ahead 2-1 at 10:53 of the second.
Tampa Bay's Marc Denis made 29 saves. Florida's Ed Belfour stopped 34 shots.
Horton missed out on a great scoring chance in the opening minute when he couldn't handle a pass while alone just outside the crease.
After Craig scored off a backhand pass from behind the net by Andreas Karlsson at 2:15, Horton tied it at 1 on a slot wrist shot at 5:30 of the first.
Denis had a diving glove save on Olli Jokinen's right-circle shot during a power play in the second. He also stopped Horton on a breakaway during the first.
Belfour turned aside Vincent Lecavalier's in-close rebound shot in the second. Lecavalier extended his point streak to five games (six assists, 11 points) with an assist on St. Louis' goal.
Notes: Montreal, which might try to add a goalie before the trade deadline, had a scout at the game. ... Florida C Jozef Stumpel (shoulder) returned after missing five games. ... Lightning RW Ruslan Fedotenko was in the lineup after missing practice Monday with a thigh injury. ... Craig Anderson, recalled from AHL Rochester on Monday, served as Belfour's backup. Alex Auld was unavailable due to left knee soreness.