He scored his second goal this season by sneaking the puck past Tampa Bay net-minder Karri Ramo at 17:07 in the third before a crowd at the net.
Washington's other goals were scored by Dave Steckel after an assist by Bradley in the first, and Brian Pothier, whose fourth tied the contest 2-2 at 17:42 of the third.
Olaf Kolzig stopped 18 of 20 shots for the Capitals, who snapped a three-game losing streak.
Vincent Lacavalier scored both Tampa Bay goals in the first and second periods, giving him 25 this season.
Ramo was beaten three times on 31 Washington shots for the Lightning, who have lost five of their last six games.
On the power play, Washington went 0 for 4 while Tampa Bay was 0 for 1.