Ruslan Fedotenko, Paul Ranger and Vincent Lecavalier, into an empty net, had third-period goals to go along with a second-period goal from Martin St. Louis as the Lightning (16-17-2) won for the second straight game. Dany Heatley and Antoine Vermette scored for the Senators (17-18-1), who continue to struggle, having lost two straight and six of their past eight.
Fedotenko beat Ottawa's Ray Emery from well out for his ninth goal of the season at 2:30 of the third period.
The Lightning had several good chances before Ranger got his first goal of the season at 8:53 of the period. Brad Richards won a faceoff right back to Ranger, who fired a shot past Emery from the point.
The Lightning had a great opportunity to increase their lead with seven minutes to play but Emery stoned St. Louis on a breakaway.
At the other end of the ice, Marc Denis was not busy, facing only 18 Senators shots.
The Lightning peppered 30 shots on Ottawa's goal, and outshot the Sens 12-6 in the third period.
After trudging through a scoreless opening period, the Senators took a 2-1 lead into the dressing room after 20 minutes.
Heatley opened the scoring with his 20th goal of the season. On a power play, Daniel Alfredsson made a perfect pass through the crease to Heatley, who shot into an empty net.
The Lightning got that goal back a little more than three minutes later when St. Louis banked a shot off the post and then Emery and in for his 23rd goal of the season.
Notes: Heatley's second-period goal was the 150th of his career. . . . The Senators play their final game before Christmas Saturday afternoon in Philadelphia. . . . The Lightning host the New York Rangers Saturday before they break for the holidays.