— So much of the Washington Capitals’ success in the postseason has stemmed from their ability to protect and hang on to even the slimmest of margins regardless of the adversity they faced. At a certain point, though, there was bound to be a break that went against them.

On Monday night at Madison Square Garden it came in the form of a high-sticking call and double-minor penalty on Joel Ward late in the third period as Washington protected a one-goal lead.

The New York Rangers scored twice on that power play — Brad Richards to force overtime, then Marc Staal 1 minute 35 seconds into the extra session — to secure a 3-2 victory and a three-games-to-two lead in this Eastern Conference semifinal series.

“It’s a game of inches. It happens pretty quick. We were a few seconds [away from] winning and it turned into an overtime and then a loss just like that,” Ward said. “It’s a little mentally disturbing for sure right now. It’s tough to be in that position when you’re letting the team down.”

Washington had been nursing a 2-1 lead since John Carlson’s power-play tally 4:20 into the third period. The Rangers pulled Henrik Lundqvist (16 saves) for an extra attacker with 1:20 to go, but with 22 seconds left they gained another when Ward received four minutes for high-sticking rookie Carl Hagelin. Heading into that penalty kill, the Capitals’ short-handed unit had been superb, not allowing a single shot on New York’s first three power plays.

Rookie Braden Holtby stopped two rapid-fire shots by Ryan Callahan with his right pad and tried to trap the puck with his glove but didn’t beat Richards to it on the 6-on-4. The Rangers’ veteran center managed to poke it past Holtby’s glove, under his pad and into the net, tying the score at 2 with 7.6 seconds remaining in regulation.

“It’s a real tough pill to swallow with six seconds left,” defenseman Karl Alzner said. “But going before that, we should’ve iced the game with eight minutes left. We had a breakaway, we had a three-on-one, two two-on-ones and we didn’t get a shot off. It’s a big mistake by us.”

With New York’s power play carrying into the overtime period, Rangers fourth-liner John Mitchell won a faceoff against Matt Hendricks in the Capitals’ zone back to Staal. The blue liner teed up a snap shot that went off of Brooks Laich and found its way past Holtby, who was screened by Carlson, as well as New York’s Derek Stepan and Artem Anisimov.

“I didn’t see a thing,” Holtby said. “So, whether I had a lane or not I’d have to look at it on video to see if I could have done a better job seeing around the traffic. That’s what happens when we play a style where we block a lot of shots; sometimes those go in.”

It was a gut-wrenching swing for the Capitals, who were fewer than seven seconds away from returning home for Game 6 Wednesday with a chance to clinch a series victory.

Instead, they could do little to quell the surge of momentum for New York, which put bookends on the contest with a strong start and even better finish.

The Rangers opened with heavy hits and made sure that every trip across the offensive blueline included a shot on Holtby. They wound up outshooting Washington, 17-4, in the first period but would only have a 1-0 lead to show for it.

Defenseman Anton Stralman scored on a bad-angle shot 10:44 into the first to give New York the all-important first goal. The Capitals have yet to win a game this postseason in which they don’t score first (0-5).

In the second, Laich snapped an eight-game scoring drought at 8:15 to even things at 1 when his shot from the slot beat a screened Lundqvist.

Then in the third, Carlson sent a booming shot past a stickless Callahan to make it 2-1 less than five minutes into the frame.

The lead allowed the Capitals to do what they’ve done so well throughout this postseason — focus on defending, minimizing mistakes and supporting Holtby for the remainder of the contest. This time, though, that wouldn’t be enough to prevent the penalty by Ward and the game-changing momentum shift that came with it.

“It’s tough. It’s hard to swallow. But it’s a hockey game,” Hendricks said with a heavy sigh. “I don’t have a lot to say about [it]. But it’s a tough loss. We need to regroup. They won at home, now we need to win at home.”