His second overtime goal in three games gave the Panthers a 3-2 victory over Atlanta on Saturday night and extended their winning streak to four games.
"It's a huge win for us," said Horton, who gave the Panthers a 1-0 victory over Boston on Tuesday. "We need to keep this thing rolling, keep getting points."
The Panthers, who have matched their season high with their four-game streak, moved into a tie with Washington for 10th place in the Eastern Conference with 72 points. Philadelphia is in eighth with 78 points.
The Panthers haven't made the playoffs since the 1999-2000 season.
"We lose, we know we could be out and not have any chance," Horton said. "So we just need to keep winning. That's all we can control is winning games."
Brett McLean added two power-play goals for Florida. Both bounced in off Atlanta players.
Kovalchuk has scored in all five games this season against the Panthers.
But it was Kovalchuk who sat in the penalty box when Horton scored. He was called for hooking Jay Bouwmeester at 3:18 of overtime.
"We played pretty good early, we battled hard, we had a couple chances late," Kovalchuk said. "It was just a bad penalty by me and they scored the game winner."
Horton scored during 4-on-3 play during overtime when he put a slap shot from inside the top of the left circle over Kari Lehtonen's left shoulder.
Florida, which rallied from a 2-0 deficit, dominated overtime with a 6-1 shots advantage.
Florida went back to All-Star goalie Tomas Vokoun after backup Craig Anderson played three straight games, including recording back-to-back shutouts on the road. Vokoun finished with 25 saves after giving up a goal on his first shot.
Lehtonen stopped 38 shots for Atlanta but lost his ninth consecutive decision since a 3-2 shootout victory over Washington on Feb. 13.
"It's just frustrating," he said. "I don't even remember when I won a game last. There's only so much you can take of this. I just need to battle and come back strong back next game."
Little opened the scoring 2:12 into the game after Mark Recchi's pass from behind the net got past Vokoun.
Kovalchuk doubled the Thrashers' lead when his one-timer trickled through Vokoun's legs.
"The second goal was a straight shot from the blue line," Vokoun said. "I would stop that most nights with my hands tied behind my back."
Florida made it 2-1 at 18:32 of the first. Lehtonen made a pad save on McLean's wrist shot, but the rebound bounced in off the skate of Thrashers defenseman Ken Klee.
McLean scored again at 8:40 of the second when his flip from the back of the net went in off the back of Lehtonen's leg.
The comeback from a two-goal deficit was the Panthers' first since Jan. 2.
"The way we played in the first period was a little embarrassing," Florida captain Olli Jokinen said. "[Vokoun] has been carrying us the whole year, and the way we played in the first is not the way you should play in front of your No. 1 goalie. It was a big win for him and for our hockey club."
Florida also won four in a row from Nov. 19-28. ... Jokinen's assists on Florida's last two goals made him the Panthers' career leader with 230. Robert Svehla had held the mark. ... Atlanta C Todd White missed his second consecutive game because of a shoulder injury sustained Wednesday against Carolina. He had missed the previous two games because of an elbow injury. ... Florida is still without C Chad Kilger, who has been suspended by the team for not returning in a timely fashion after being granted a leave of absence.