J.R. Smith may have more graffiti on him than a New York subway car. He may have the most regrettable driving record in the NBA (one wreck of his making ending in a fatality). He may have been labeled by some of his former employers as more self-absorbed than a Westminster show poodle.

Just don’t give him an inch of daylight in which to launch that jumper that has no conscience. He has a reputation, too, for making a good number of those.

Wednesday night the enigma that is Earl Joseph Smith III went off on the Hawks. He was the man with the history of trouble but a very secure handle on the moment. He was the man, even more than the redoubtable LeBron James, who took up the shovel and dug the 0-1 Eastern Conference final hole the Hawks now occupy.

Scoring a personal postseason career high 28 points, hitting a Cleveland playoff record eight 3-pointers (on a dozen attempts), Smith was the Cavs X factor that stunned the Hawks. James got his — 31 points — but it was Smith’s second-half outburst that ultimately provided the Cavs with the winning cushion.

“When (Smith) gets hot, he gets smokin’ hot,” said David Blatt, the happy Cavs coach.

“He was terrific. Probably overlooked in his great shooting performance ws the fact that he defended as well as he did and he got eight rebounds,” Blatt said.

The reaction from the other side was understandably more subdued. “He did make a handful of tough shots, but he’s a shooter,” Hawks coach Mike Budenholzer said. “He’s somebody who can get hot and he was a priority coming into the game. I think we can do a better job and not have the breakdowns going into the next game.”

Smith did his greatest damage over a less than five-minute span that bridged the third and fourth quarters. It was a two-point game with just under three minutes left in the third when Smith went from hot to nuclear.

By the time 90 seconds had elapsed in the fourth quarter, after Smith had hit five 3s and assisted on an ally-oop dunk by Tristan Thompson, the Cavs led by 15, 82-67. Cleveland held on from there to win Game 1 97-89.

That last assist said much about Smith’s growth in Cleveland. “It’s kind of hard when hitting the shots I was hitting to pass the ball,” Smith said, “but you got to find a way.”

The New York Knicks dispatched Smith and Iman Shumpert to the Cavs in January, a move that initially stirred some concerns over how he would affect the Cleveland chemistry. But instead of creating chaos, Smith often stood out as he did Wednesday night — the most effective member of the LeBron James backup singers.

His citizenship in Cleveland has been mostly exemplary. His only slip-up to date came in the rough and tumble playoff series finale against Boston when he threw a backhand that caught Jae Crowder in the face. He drew a two-game suspension for that slip.

“A Godsend,” Blatt has consistently called Smith.

A beneficiary of James’ calming influence, others have noted. Including James himself.

“I understand he’s misunderstood, how everybody perceives him,” James told reporters before the Cavs left for Atlanta. “I understand that, so I’m able to relate to him. I’m able to be a big brother to him and give him the tips on trying to be the best teammate he can be, the best father he can be, the best friend he can be.”

And, now comes this addendum to Smith’s complex reputation: A Hawks nemesis of the first order.