Braden Holtby made 26 saves - half of them in the third period and eight of them while the Lightning was enjoying one of its seven power play opportunities - and Dmitry Orlov supplied the game-winner late for the second time in as many home games against the Lightning this season.
With the game tied at 1-1 in the back half of the third, Washington weathered an extended two-man advantage with two of its most trusted penalty killers in the box. Less than a minute after they did so, Orlov scored what would prove to be the game-winner.
"The penalty kill," says Caps coach Todd Reirden. "That was the story of the game for sure. A huge 5-on-3 kill, then a 6-on-4 kill [with the Lightning goalie pulled]. Sacrifice from all of our guys who were out there in that situation, and then tremendous goaltending.
"To be able to shut a team down like that is a challenge anytime - 5-on-3 against anybody - let alone that group. I'm really, really happy with our guys tonight for their penalty kill."
Thanks to Radko Gudas' first goal in a Caps sweater early in the second period and some staunch defensive play at 5-on-5 over the game's first 40 minutes, Washington was able to take a 1-0 lead into the third period.
Video: TBL@WSH: Gudas scores first goal with Capitals
Holtby had a relatively quiet first 40 minutes, facing only eight shots on net at even strength. But he made a strong stop on Nikita Kucherov in the front half of the first, and soon after a couple of good-looking blocker saves on Victor Hedman and Steven Stamkos during the Lightning's first power play look.
Washington put on a clinic on its own first man advantage of the night, holding the zone with a series of impressive recoveries and keeps, and generating a handful of glorious looks at veteran goaltender Curtis McElhinney and the Tampa Bay net. But T.J. Oshie, Alex Ovechkin and John Carlson all missed the net, keeping the game scoreless after 20 minutes of play.
Gudas staked the Caps to a 1-0 lead at 4:40 of the second, firing a shot from center point that found its way past McElhinney.
The defenseman's first goal as a Capital came with his dad in attendance, and against his former team.
"It felt great," says Gudas. "I didn't think it was a particularly great shot, but it hot somebody at the net front, so really fortunate that it went in."
Five of Washington's seven minor penalties came in the second half of the contest, putting the Caps' slim lead in peril. The Lightning entered the game third in the league in scoring and with the circuit's third-ranked power play, but the Caps killed all seven, a total of 11:05 in shorthanded time and 86 seconds worth of a two-man disadvantage.
Video: Postgame | December 21
Kucherov scored on a broken play exactly halfway through the third, tying the game at 1-1. Within 35 seconds, the Caps were in penalty trouble when Nick Jensen - one of Washington's most deployed defensemen on the kill - took a rare minor penalty. Seconds later, the soup got hotter when Lars Eller - another shorthanded stalwart - went off for delay of game.
With Tom Wilson as the lone forward and with Jonas Siegenthaler and John Carlson in the back, the Caps killed the front half and Carlson, Jensen, Carl Hagelin and Nicklas Backstrom combined to take care of the rest of it. All the while, Holtby was in control, swallowing up every shot and keep any loose change away. As he has done on many occasions this season, he did not give up a late goal that would put Washington behind.
"We made it a little harder on ourselves that we needed to," says Gudas of the Caps' propensity for taking penalties, "but I thought we stuck with it. We made smart plays, we didn't really turn the puck over too much, and I thought we deserved it tonight."
When Eller was released from the box, the crowd erupted, and the Caps seemed to find the energy to retake the lead. Less than a minute after completing those kills, Evgeny Kuznetsov and Jakub Vrana combined to set up an Orlov one-timer from the left point. Orlov caught all of it, sending a laser through traffic and past McElhinney for a 2-1 Washington lead with 6:03 left.
"Our forwards did a good job of getting the puck in the zone and trying to keep the puck," recounts Orlov. "If they don't have a chance, they give it to us and just try to crash the net. We just try to get the puck there, and I think it's the most important thing right now in this league, to get the puck through."
The Caps made it interesting, taking two more minor penalties after Orlov's go-ahead goal. When the Bolts opted to pull McElhinney with just under three minutes remaining to gain a 6-on-4 skater advantage, Nic Dowd scored a shorthanded goal into an empty net to give the Caps the breathing room needed to seal the deal.
Video: Reirden Postgame | December 21
"I can't sit here and say we played very well," laments Lightning coach Jon Cooper. "I can't say that about our team in the last month and a half. It was two tough periods for us, and McElhinney kept us in it.
"I've got to give the guys credit; we came out and had a strong third, and we tie it. And then we get a minute and a half of a 5-on-3 with the game on the line. We've got to close it out there. We found a way not to, and they found a way to win."
Through their first 35 games of the season, the Caps never had a contest in which two different defensemen scored. They have now had goals from two different defensemen in winning each of two games in the last two nights, so they continue to find new ways to win.
"It was two times the goalie didn't see the shot, and we score," says Orlov. "So it's a good game, and a good win, back-to-back."