The Panthers rallied from a 2-1 deficit in the third to beat the Capitals 4-2.
"It was no big deal, there was plenty of time left," Florida defenseman Jay Bouwmeester said. "Everyone knew it was a big game. To be able to come back is a little bit of a confidence boost for us."
Kreps broke the tie at 8:27 of the third period, when he fired the puck from behind the net. It went off goalie Brent Johnson's skate into the net.
"I saw [Johnson] out of position a little bit," Kreps said. "I tried to put it in front. It was a lucky goal."
Florida ended a two-game losing streak with their first victory since Richard Zednik's frightening neck injury last Sunday.
"You look at how big this game is, a lot of guys were battling," Vokoun said. "I think everybody played hard and we got rewarded."
Rostislav Olesz also scored for the Panthers, who tied Washington for third place in the Southeast Division with 60 points, only two behind co-division leaders Carolina and Atlanta. Tampa Bay is last in the division with 56 points.
"You look at the standings, there are five teams maybe fighting for one spot," Vokoun said. "There's less margin for error than in the playoffs. In the playoffs you have to lose four games to get knocked out; now when we lose it gets magnified all the time because we play each other."
Tomas Fleischmann gave Washington the lead 57 seconds into the third when his seemingly harmless wrist shot from just inside the blue line beat Vokoun to the glove side.
"It was just a bad goal," Vokoun said. "He kind of surprised me with the shot."
Horton tied it at 3:57, when he grabbed a deflection and put the puck past Johnson from a sharp angle.
"We didn't have the lead long enough," Capitals coach Bruce Boudreau said. "If we had held the lead longer we may have gotten them out of their game, but they came right back and scored within three minutes."
Alexander Semin also scored for the Capitals.
Alexander Ovechkin, the NHL leader in goals and points, was held without a point. He came in with nine goals in his previous seven games.
"I don't know if they did anything to Alex at all," Boudreau said. "He might just not have played his best. He's played great for 57 games, I think we've got to cut him a little slack."
Ovechkin finished with four shots on goal, and his best scoring chance came in the third period on a quick wrist shot from the faceoff circle.
"We know where he is all the time," Bouwmeester said. "You have to be good defensively, but you have to be a little lucky, too. We did a decent job of limiting his chances."
Vokoun stopped 30 shots for Florida. Johnson made 25 saves.
Olesz, who missed the previous 12 games because of a hand injury, opened the scoring at 5:52 of the first period. He followed his own shot and beat Johnson with a backhand.
Semin tied it 1:12 into the second period with Washington's first power-play goal in six road games. He grabbed a rebound in front of the net and backhanded the puck over a sprawled Vokoun.
"Not taking anything away from them, they played hard, the other team," Boudreau said. "Tonight I thought for the most part we beat ourselves."
Florida is 4-2 against Washington this season. The Panthers have won the season series the last four seasons. ... Sixteen Capitals players fathers or fathers-in-law joined the team for Washington's trip to Florida and Tampa Bay. ... Washington was held to one shot in the first 12:40 of the game. ... Capitals D Tom Poti sat out the game because of a leg injury he sustained against Atlanta on Wednesday night.