Atlanta took its first lead of the night on Johnson's dunk with 1:53 remaining. Andre Iguodala missed a tough 3, Josh Smith rebounded and fired a long pass to his teammate breaking free at the other end.
Then, with the Hawks clinging to a 90-88 lead, Johnson got the ball at the top of the key with everyone in the building expecting him to shoot. He bounced off Thaddeus Young and put up a 32-footer before Andre Miller could work around a pick, the ball hitting nothing but net.
This was like two different games.
Philadelphia was unstoppable in the first half, especially Young. He had 17 points by the break, including 3-of-4 from beyond the 3-point stripe.
The 76ers outhustled the Hawks, building a 20-8 rebounding edge at one point, and Atlanta couldn't make anything. Starting forwards Smith and Marvin Williams combined to go 0-for-11 over the first two quarters.
Iguodala's jumper with 7½ minutes remaining in the second period boosted Philadelphia to a 44-21 lead. The Hawks showed a bit of life before halftime, but still trailed 57-44 heading to the locker room.
A different team returned to the court. Atlanta got the deficit to single digits heading to the fourth quarter, then outscored the 76ers 29-13 over the final 12 minutes.
After missing his first seven shots, Smith bounced back to make six of his last nine - including a pair of crucial 3s - to finish with 14 points.
But Johnson was the go-to guy all the way. He shot 14-of-23 from the field, hit a couple of 3s, made all five of his free-throw attempts and even found time to dole out five assists.
Mike Bibby added 19 points for the Hawks, and Zaza Pachulia came off the bench to add some much-needed defensive toughness. The burly center picked off eight rebounds in 21 minutes.
Young led the 76ers with 22 points, but only five came after halftime. All five Philadelphia starters scored in double figures, including Elton Brand with 17 points and Iguodala with 16. Brand also had 16 rebounds.
Notes: The game drew a sellout of 19,651. ... There were technicals galore. Both coaches, Atlanta's Mike Woodson and Philadelphia's Maurice Cheeks, were whistled, as were Reggie Evans of the 76ers and Hawks assistant coach Jim Todd. ... Smith led the Hawks with 11 rebounds. Atlanta cut into Philadelphia's early advantage on the boards but was still outrebounded 48-41.