Lewis made a 3-pointer with 14.7 seconds left and the Magic, who dethroned the champion Celtics in the previous round, survived two shots by Cleveland in the final seconds. Mo Williams missed a catch-and-shoot jumper off a jump ball as the horn sounded and the Cavaliers fell to 8-1 in the postseason.
"It's a big victory," said Howard, who broke one of the shot clocks with a dunk in the opening minutes. "We kept fighting the whole game. We kept believing we could win."
Game 2 is tomorrow night at Quicken Loans Arena, which fell eerily silent after the Magic's win.
As fans headed to the exits, they turned to observe James still on the floor and bent over in obvious pain. He seemed to be bothered by cramps in the fourth quarter and was tended to by Cleveland's training staff before slowly making his way to the locker room.
Cleveland, coming off its second extended layoff of the playoffs after sweeping Atlanta, lost its grip on the game with a stagnant third quarter that carried into the fourth.
Orlando took its first lead at 85-84 with 10:06 left when Anthony Johnson hit a 3-pointer from the left corner. The bucket seemed to suck the air out of the raucous building and Cleveland coach Mike Brown quickly called a timeout to stop the Magic's run.
The Magic, though, kept making big shots with Lewis hitting a jumper with 31.6 seconds left to give Orlando a 104-103 lead.
"You got to play 48 minutes," Lewis said. "The most important thing is to play 48 minutes. We played only one half but it was the second half."
