SAN ANTONIO — San Antonio is halfway to turning the Western Conference finals into a runaway.

Tony Parker scored 34 points, Manu Ginobili added 20 and the Spurs stayed perfect in the playoffs with a 120-111 win over the Oklahoma City Thunder in Game 2 on Tuesday night.

The Spurs set an NBA record with their 20th consecutive victory bridging the regular season and the playoffs. They came in sharing the longest such streak with the 2000-01 Lakers, who won 19 straight before losing to Philadelphia in the first game of the finals.

Those Lakers went on to win the championship and there’s no reason yet to think the Spurs won’t do the same. They put on an offensive clinic for three quarters, shooting 60 percent from the field and leading by as many as 22 points in the third quarter.

Parker finished with eight of the Spurs’ 27 assists, and San Antonio went 11 for 26 from 3-point range. The Spurs went only 10-for-23 from the field in the fourth quarter and still shot 55 percent for the game.

“Sometimes, it’s exactly as we drew it,” Spurs coach Gregg Popovich said of the offense. “Other times, it’s a miracle, and that’s the truth. It doesn’t always go exactly the way you planned. Good players get it done.”

The Thunder made a late surge to get within six points, but Parker, Ginobili and Tim Duncan helped San Antonio finish off the Thunder for a 2-0 lead heading into Game 3 Thursday night in Oklahoma City.

Kevin Durant had 31 points and James Harden rebounded from a rough Game 1 to score 30 for the Thunder, who have lost two straight for the first time since early April. Oklahoma City dropped to 15-4 in games after losses this season.

“Our guys played hard,” Thunder coach Scott Brooks said. “Unfortunately, we came away with nothing the last few days.”

San Antonio picked up where it left off from the 39-point fourth quarter that turned Game 1 on Sunday. With sharp passes and hot shooting, the Spurs jumped to a 19-9 lead after the Thunder missed six of their first seven shots and had three turnovers in the first 4 minutes.

The Spurs shot 52 percent (12 for 23) in the opening quarter, though, and led 28-22. Durant was on the bench at the start of the second quarter, and Parker and the Spurs put together a 14-4 spurt to stretch the gap to 13 points.

Russell Westbrook hammered Parker’s arm on a drive and he crumpled to the court. That didn’t faze Parker, who scored the Spurs’ next seven points to keep San Antonio rolling.

The Spurs shot 58 percent (22 of 38) and had 13 assists in the first half. They also cut down their turnovers, committing only six in the first half after giving away 14 in the first two quarters of Game 1.

“You never go out and say, ‘We’re going to start out fast,’” Popovich said. “You don’t know what is going to happen. You just want your team to be aggressive. Good teams are aggressive and it is, it’s a matter of making shots or not making shots.”

The Spurs resumed picking apart Oklahoma City’s defense with precision passes after the break, scoring on five straight possessions. San Antonio was shooting 63 percent from the field and 64 percent from 3-point range at one point (7 for 11).

The biggest cheer from the crowd came after Ginobili flipped a behind-the-back pass to Parker in the corner for another 3 and the lead ballooned to 78-58.

Late in the third quarter, the Thunder began intentionally fouling Tiago Splitter, a 32 percent free-throw shooter during the playoffs.

That backfired, too. Splitter went 5 for 10 over a 54-second span before Popovich replaced him with Duncan, and Oklahoma City trailed by the same margin — 16 — that it did when Brooks called for the “Hack-a-Splitter” strategy.

It may not have showed on the scoreboard, but the Spurs seemed to lose their edge after that.

“There’s a reason why you do it, to kill the rhythm,” Parker said. “I think it got us out of our rhythm.”

Parker returned with 10:58 left and San Antonio leading 92-78, but he was shaky on offense for the first time. Gary Neal promptly curled around a screen and swished a 3-pointer, the Spurs’ 10th of the game.

Parker, Ginobili and Duncan were on the court together at the 8-minute mark, after the Thunder cut the deficit to eight. Ginobili’s floater in the lane was only the Spurs’ third field goal of the fourth quarter and put San Antonio up 99-89.

The Thunder had the deficit down to six with just over 5 minutes remaining. The Spurs missed 12 of 15 shots during one stretch, but Parker hit an off-balance, high-arcing jumper with 3:39 left for a 107-96 lead and San Antonio controlled the game from there.

At least now, the Thunder get to return home, where they went 26-7 in the regular season. But only 14 teams in NBA playoff history have overcome 2-0 deficits to win series, and the Spurs show no signs of letting the Thunder back in it.