It was a slow, painful loss, one that could haunt the Lakers if their playoff run ends soon.

They were ahead by 11 in the third quarter and then they weren’t as Denver Nuggets guard Jamal Murray dominated down the stretch and the Lakers’ offense evaporated into the thin mile-high air.

The net result was a 108-103 Denver victory Thursday over the Lakers in Game 2 of the Western Conference finals.

The Lakers trail the series, 2-0, though Games 3 and 4 are at Crypto.com Arena, where the Lakers are 7-0 this postseason.

It looked like the Lakers could steal a road victory thanks to an unexpected contribution from reserve forward Rui Hachimura, who made his first eight shots and jump-started the offense.

The Lakers were also buoyed by Murray’s dreadful shooting — 5 for 17 through three quarters.

Unfortunately for the Lakers, there are four quarters in an NBA game.

Murray scored 23 points in the fourth, draining four three-pointers and making seven of eight free-throw attempts. He finished with 37 points.

Denver center Nikola Jokic, the star of Game 1, went scoreless in the fourth quarter. He didn’t need any points. Murray was that good.

Denver coach Mike Malone seemed almost defensive after the Game 2 victory, poking at what he implied had been a pro-Lakers national narrative.

“You win Game 1…and all everyone talked about was the Lakers. No one talked about Nikola just had a historic performance,” Malone said. “So you put that in your pipe, you smoke it, and you know what, we’re going to go up, 2-0.”

Jokic, by the way, still had fine stats in Game 2 — 23 points, 17 rebounds and 12 assists.

It’s just that Murray, who missed all last season while rehabbing from a torn ACL, was the headline in Game 2.

“He made shots at the end of the clock when we guarding for 24 seconds. He had his three-point shot going in the fourth,” LeBron James said. “It’s no surprise. He’s done it before.”

The Lakers, meanwhile, hadn’t lost back-to-back games in more than two months.

James struggled from three-point range, missing all six of his tries from deep, and Anthony Davis misfired from just about everywhere, making only four of 15 shots.

“I got the same looks. Lot of them were just short tonight. I’ll be back,” in Game 3, Davis said.

James had a bizarre first half where he missed an uncontested lay-up and fumbled the ball while gearing up for a reverse dunk with no defenders ahead of him on a fastbreak.

The second error really bothered him.

“It sucks that ball squirted out of my hands, maybe hit my knee or something,” James said. “Unforced turnover on myself. Horrible. Especially on the road.”

Still, James was close to a triple-double, finishing with 22 points, nine rebounds and 10 assists. Davis scored 18 points.

Hachimura scored 21 points after barely being part of the West semifinals against Golden State, experiencing quiet nights where he scored two, four and five points.

This series has been a different story for Hachimura. It looked like he would be the catalyst for a Lakers victory Thursday until Denver got hot late, making five consecutive three-pointers to take the lead for good.

The Lakers must win the next two games at home, just like they did in their first two playoff series.

James tried to sound upbeat.

“This is not the NCAA tournament. It’s the first team to four wins,” he said. “We have an opportunity to go home and play great basketball.”