NEW YORK — For the first time in NBA Finals history, a sitting U.S. president was in the building to watch. And for what only seems like the first time in history, the Knicks finally lost a playoff game.With President Donald J. Trump, a New Yorker, in the Madison Square Garden audience, the Knicks fell in Game 3 to the San Antonio Spurs, 115-111, snapping a 13-game winning streak that lasted for more than a month.Victor Wembanyama, knowing no team has come back from a 3-0 deficit in an NBA playoff series, didn’t need to find out if his Spurs could do it. He scored 32 points in the win.The Knicks still lead the series, 2-1, and host Game 4 on Wednesday. Monday night was the first finals game at the Garden since 1999. New York hasn’t won a championship since 1973.Wemby had his best game so far in this series, connecting on 11 of 18 shots to go with eight rebounds, six assists and three blocks. Stephon Castle added 23 points, including two crucial free throws late, and Dylan Harper contributed 13 points and nine rebounds off the bench.The Knicks received 32 points from Jalen Brunson and 28 points from OG Anunoby. Jordan Clarkson, who didn’t play at all in Game 2, scored 10 points off the New York bench. Karl-Anthony Towns, a hero of Game 2, shot just 4 of 10 and finished with 11 points.The charged atmosphere at the Garden — where chants of “U-S-A!” broke out before the national anthem — cranked up a notch when Trump was shown on the video board standing at attention and was booed lustily by the home crowd. Trump seemed to smirk in response to the boos before Garden board operators replaced him with Brunson.San Antonio led 33-22 after one quarter and were ahead by 12 in the first half before the Knicks found their footing. A furious second quarter from Anunoby (11 points) and Brunson (10) helped New York soar past the Spurs and take a 64-57 lead into halftime. The Knicks outscored their counterpart by 21 in Anunoby’s nine minutes on the court in the second — with two of his points coming after he beat Wembanyama off the dribble for a dunk.The Spurs pulled back ahead in the third quarter and traded baskets over a furious final two minutes. Harper answered a Clarkson 3-ball with 33.5 seconds left for a 92-89 lead that was trimmed to one heading to the fourth. Brunson picked up his fourth foul with 4:29 remaining in the period.The Spurs held leads in each of the first two games in the fourth quarter at home but couldn’t hold on. Castle’s 3 with 1:53 left put the Spurs ahead, 111-104, and helped them stave off yet another comeback.Brunson connected on a 3 with 33.7 seconds remaining but De’Aaron Fox (12 points) answered with a critical stepback jumper with 12.2 seconds left for a five-point advantage. Anunoby’s 3 in the corner with 9.4 seconds made it 113-111 Spurs, and Castle made two foul shots with 6.8 seconds remaining.