Jaromir Jagr scored two goals and Dan Ellis made 25 saves as the Panthers won 4-2 on Sunday, and pulled within a point of the Senators for ninth place in the Eastern Conference.
"It's our line's job to score goals, and luckily we did it," Jagr said. "This was a Game 7 for us and now we have to get ready for the next Game 7 against Boston (on Tuesday)."
The Bruins currently hold the final playoff spot in the East, three points up on the Senators following a 2-1 overtime win over the Carolina Hurricanes on Sunday.
Jussi Jokinen and Dave Bolland also scored for Florida, while Erik Karlsson and Jean-Gabriel Pageau had goals for the Senators, who have lost three straight and four of five. Ottawa's Craig Anderson made 33 saves.
"They have to be able to fight their way through it," Senators coach Dave Cameron said of his team's sudden rough stretch. "We've been pushing and have had a lot of Game 7's lately and it's probably taking its toll. It's that time of year."
Trailing 2-0 entering the third period, Karlsson got the Senators on the board with a power-play goal at 4:43. It was just the second time in the last 34 opportunities at home that Ottawa converted on a power play. Karlsson took a shot from the point that found its way through four players and past Ellis.
After drawing Anderson out of the net with a fake shot, Jagr scored his second goal of the game at 13:57 on a wraparound to give the Panthers a 3-1 lead.
Pageau scored at 17:39 for the Senators before Bolland iced the win for Florida with an empty-net goal.
"It was a big game for us obviously," Florida coach Gerard Gallant said. "It's a tight race and we want to stay in that race so we had to win, so we're staying around."
After a scoreless first period, Florida took advantage of Ottawa's penalty troubles in the second by scoring twice with the man-advantage.
Jagr opened the scoring at 7:36 when he cut to the front of the net and beat Anderson through the legs with a shot from the hash marks.
That goal came with Senators defenseman Eric Gryba in the penalty box for interference. Gryba was again in the box, this time for roughing, when Jokinen scored at 15:49 to give the Panthers a 2-0 lead.
Jokinen was in the slot when he took a pass from Bolland and fired a shot past the glove hand of Anderson.
"It was one of those games where it went back and forth," Anderson said. "There were times when it seemed like we couldn't get anything going and there were other times we were taking it to them pretty good and didn't get rewarded."
The Senators did have some chances in the first period, but Ellis made big stops off Alex Chiasson and Pageau in close and also got some help as Mark Stone hit the crossbar.
NOTES: Milan Michalek, Zack Smith, Matt Puempel and Patrick Wiercioch were scratches for Ottawa. ... Shawn Thornton, Brad Boyes, Nick Bjugstad and Al Montoya were scratches for the Panthers. ... Chiasson reached century mark for penalties with his first of two minor penalties. He now has 103 penalty minutes. ... Florida leads the NHL in one-goal games with 47.