No lead is safe when the Hawks and Celtics play.

The Hawks erased a 12-point fourth-quarter deficit to force overtime. The Celtics overcame a four-point deficit in the extra period.

After a Hawks turnover, one of several down the stretch, Jason Terry drained a 3-pointer with 35 seconds to break a tie. After another Hawks’ turnover, their second straight, Terry sank two free throws to seal the 107-102 victory at the always raucous TD Garden.

“Late, particularly in the overtime, we made too many bad plays on both ends of the floor,” Hawks coach Larry Drew said. “We were right there but in this league, at this level, it comes down to making plays. They made plays and we did not.”

The Hawks were expecting a playoff atmosphere and, boy, they got it.

A brief falter to start the final quarter led the Hawks’ double-digit deficit. After Devin Harris’ basket to start the fourth period pulled the Hawks to within two points, 72-70, the Celtics went on an 8-0 run. The streak was added by four straight misses on Hawks’ possessions. The lead would grow to as many as 12 points.

However, the Hawks stormed back and tied the game, 92-92, on a 3-pointer by Kyle Korver with 1:31 remaining.

The Hawks led 98-94 in the extra period before the Celtics rallied with the help of 3-pointers by an open Jeff Green (which bounced high off the rim), Paul Pierce and Terry.

After Smith tied the game 102-102 with a free throw, the Hawks got the ball back on a Terry offensive foul. However, Smith had the ball stolen setting up Terry’s game-winner. Another pass intended for Al Horford sailed out of bounds before the final free throws.

“We buried ourselves,” said Smith, who finished with a season-high 32 points Smith. “I had a couple of turnovers that I wish I could have had back.”

On the final turnover, trailing by three points with 30.9 seconds left, Horford said he was expecting a lob pass.

“It was just a miscommunication,” Horford said. “I thought Josh was going to lob it. It didn’t come off my hands. I didn’t get a chance to put them up. (Kevin Garnett) tapped it and it hit my head. That was a tough call but before that we had too many turnovers.”

The Hawks (34-27) fell for the fourth time in five games. It was their first overtime loss of the season (4-1).

Drew said defensive breakdowns, particularly on the Celtics’ 3-pointers and by allowing a key offensive rebound setting up Pierce, were especially harmful.

“We knew coming into this game it was a game we had to play solid on both ends, which we did not do,” Drew said. “Defensively, we had too many breakdowns. Against a team like Boston you can’t have that many defensive breakdowns and we just had too many at crucial moments.”

Smith scored 23 points in the second half and overtime. He also tied a season-high with nine assists and had eight rebounds. Jeff Teague (26 points, nine assists) and Horford (22 points, 13 rebounds) had big games for the Hawks, who got just eight points from their bench. The three accounted for 78 percent of the offense.

The Celtics (34-27) won their night straight home game. They improved to 14-4 since losing All-Star point guard Rajon Rondo.

Pierce led the Celtics with 27 points. Terry added 19 points.

In the two previous meetings between the team this season, the Hawks couldn’t hold a 19-point lead in one defeat and overcame a 27-point deficit in a double-overtime win.

The Celtics and Hawks are tied for sixth place in the Eastern Conference. The Hawks are 1-1/2 games behind the Nets, Saturday’s opponent, for the fourth spot.

“We both knew what was at stake in this game,” Smith said. “It was a playoff atmosphere game for the both of us. We just came up short.”

The Hawks trailed by just four points, 72-68, going into the decisive final quarter. Smith scored 11 third-quarter points for the Hawks.

The Celtics took a 52-47 lead into intermission after a back-and-forth first half. The Celtics used an 8-0 run in the second quarter to build a 10-point advantage. The Hawks answered with a 13-2 run and took a brief lead with 2:46 left in the half on an Anthony Tolliver 3-pointer. The Celtics took the halftime cushion by ending with a 9-3 run.

The first half featured 11 lead changes, nine in the first quarter, and two ties.

Korver had his streak of consecutive games with a 3-pointer extended to 54. The Celtics blanked Korver, who took just four 3-point attempts, three hurried.

“It was my best look of the night,” Korver said of the game-tying shot.

The teams meet again in Boston on March 29.

“It’s a battle out there,” Horford said. “We’re fighting. And this game meant a lot. You know, they got it. But lucky for us we still have one more time. So we’ll be looking to even the series.”