Robertson’s goal came 44 seconds after Jake Sanderson tied the score 1-1. Dallas outscored Ottawa 3-1 in the second period following a scoreless first.
Johnston and Robertson share the team lead with 16 goals each, tied for fourth in the NHL. Robertson has points in 10 of his last 11 games (13 goals, 9 assists) and leads Dallas with 35 points (fifth).
Linus Ullmark stopped 20 shots for the Senators, who are 3-3-0 heading into the finale of a season-long seven-game road trip.
The Stars’ 38 points are second most in the NHL but four behind league-leading Colorado in the Central Division.
Dallas’ NHL-best power play has scored 29 times in 26 games. Last season, the Stars’ 29th power-play goal came in game No. 49 on Jan. 26.
Mikko Rantanen had a season-high three assists.
The Senators went 6-4-3 in November, their first winning mark in the month since 2016-17.
Stars defenseman Lian Bichsel left late in the second period with an apparent injury to his left leg. He went into the boards after getting hung up with Ottawa’s Fabian Zetterlund.
Up next
Senators: At Montreal on Tuesday.
Stars: Begin a road back-to-back on Tuesday against the New York Rangers.
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AP NHL: https://apnews.com/hub/nhl
The Associated Press