The Knights rallied three times from one-goal deficits before Tuch’s shot from in close. Capitals goalie Philipp Grubauer tied to corral the loose puck, but knocked it into the net with his catching hand. Washington challenged the play for goaltender interference, but the goal stood.
Nicklas Backstrom gave Metropolitan Division-leading Washington a 3-2 lead 52 seconds into the third period. Reilly Smith tied it when he scored his second goal of the game on a wrist shot from the left circle at 9:21.
Marc-Andre Fleury, who had consecutive shutouts versus Washington coming in, stopped 20 shots.
Ryan Carpenter had a goal and an assist for the Golden Knights, leaders of the Pacific Division. Jonathan Marchessault and Pierre-Edouard Bellemare each had two assists, and Tuch also had an assist.
Matt Niskanen had a goal and an assist for Washington. Chandler Stephenson scored his third goal in his last three games after netting two in his first 36.
Grubauer had 27 saves.
Both teams were coming off three-goal losses on Friday night. The Golden Knights improved to 3-1 on their three-game road trip.
Washington made it 1-0 at 7:22 of the first period when Stephenson beat Fleury to the far side with a wrist shot from the left circle. The goal ended Fleury’s personal shutout streak against Washington at 134 minutes, 53 seconds, dating to Game 6 of the Eastern Conference semifinals last year when he was with Pittsburgh.
Vegas tied it at 16:06 on play started by former Capital Nate Schmidt in his return to Washington. Schmidt carried the puck into the Washington zone and passed back to Bellemare, whose centring pass was re-directed by Carpenter past Grubauer.
The goal snapped a 27-game drought for Carpenter dating to January 2017.
Niskanen made it 2-1 in the second period when he converted a nice feed from Evgeny Kuznetsov. The Golden Knights tied it on a power play goal with 1:07 left when Grubauer stopped Smith’s first two shots in front, but not the third.
NOTES: With the win, Fleury moved ahead of Dominik Hasek for 13th all-time with 390 career wins. . Fleury stopped 26 shots in a Dec. 23 Vegas win and 29 for the Penguins in a 2-0 Game 7 win in the conference semifinals. . Golden Knights D Brad Hunt was back in the lineup, replacing D Jason Garrison. . Capitals F Jakub Vrana, a healthy scratch the previous two games, was in the lineup in place of F Alex Chiasson. . Washington had allowed the first goal in nine straight games.
Golden Knights: Play at Pittsburgh on Tuesday.
Capitals: Play at Columbus on Tuesday.