Austin Watson gave Ottawa a 1-0 lead at 4:28 of the first period while the Senators had the first nine shots of the game. Jonathan Huberdeau tied it 1-1 at 13:05 with his 10th goal of the season off a feed from Reinhart.
The Panthers have lost three of four after a three-game road trip that concluded with a 3-2 loss against the Colorado Avalanche on Sunday.
"We knew that they had a tough trip coming back from Colorado that they might be a little slow coming out of the gate and we wanted to jump real hard on them, and we did," Senators coach D.J. Smith said. "Unfortunately, it's only 1-1 after one, but tied or better after one is a good result on the road for us. And we just stayed with it and I thought it was an entire team effort."
Gambrell gave Ottawa a 2-1 lead at 1:30 of the second period on a shorthanded breakaway. Reinhart tied it 2-2 at 15:33 with a rebound before Norris gave Ottawa its third lead 33 seconds later.
Brady Tkachuk and Paul had goals on 5-on-3 power plays at 14:23 and 14:57 of the third period for the 8-2 final.
Florida was 0-for-6 on the power play.
"We're going to face adversity as a team," Panthers defenseman Aaron Ekblad said. "We know that. It's all about coming back to work tomorrow and finding a way. We know we're a good team, and we're going to find a way."
NOTES:Huberdeau and defenseman MacKenzie Weegar each left the game early in the third period after being assessed a misconduct penalty. … Panthers forward Anthony Duclair played 14:06 and had three shots in his return after missing eight games with a lower-body injury. … Ottawa became the first NHL team to score eight goals in a road game this season.