The 22-year old Stamkos became the first Tampa Bay player to have three consecutive seasons of at least 40 goals when he scored 1:50 into the second period. The center stole an errant pass at the Lightning blue line and made a nifty stick-handling move during a breakaway to beat goalie Tomas Vokoun and give the Lightning a 2-0 lead.
Tom Pyatt also scored, and Mathieu Garon made 23 saves for the Lightning.
With a win, Washington could have tied the Panthers — who have one game at hand — for first place in the Southeast Division.
Stamkos had a career-high 51 goals in the 2009-10 season and scored 45 times last season. He has three goals and two assists in his last two games.
Laich cut Washington's the deficit to 2-1 with an in-close redirection at 9:31 of the second. It was his first goal in eight games.
Pyatt put the Lightning up 1-0 on a rebound goal 2:10 into the game.
Vokoun finished with 21 saves.
NOTES: Capitals D Mike Green was back in the lineup after missing 18 games because of an abdominal injury. ... Lightning D Marc-Andre Bergeron sat out his sixth straight game, and 15th in 16, due to a back injury. ... Washington RW Troy Brouwer was held off the score sheet. In his last 20 games, all four of his goals have come against Tampa Bay in games on Jan. 13 and 31.