The Bolts held a late-game 2-1 lead but Nick Foligno pulled Ottawa even with just under 4 minutes remaining in regulation as the last-place Senators played spoilers in the Eastern Conference.
Tampa Bay, which is seeking to catch Washington atop the Southeast Division and holds the fifth spot in the East's playoff seedings, absorbed its eighth loss in 10 games.
Vincent Lecavalier and Dana Tyrell found the net and Dwayne Roloson turned aside 31 shots for the Lightning.
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