James Harden the hero as Philadelphia 76ers beat Boston Celtics in overtime

James Harden has hit the go-ahead 3-pointer with 18 seconds left in overtime and scored 42 points to help the Philadelphia 76ers stave off a wild Boston Celtics comeback in a 116-115 victory that evened their NBA playoff series at 2-2.

Marcus Smart’s potential winner was a tick too late and the Celtics now head home for Game 5 on Tuesday (Wednesday AEST).

“I just want to win,” said Harden, who also hit the floater with 16 seconds left in regulation to send the clash into OT.

“Today was do-or-die for us.”

Smart and Jayson Tatum keyed a Celtics rally from 15 points down with two minutes left in the third quarter in hopes of seizing control of the series.

The Sixers were on the brink of defeat numerous times over the final 17 minutes, none more than when Joel Embiid crashed into Smart on a driving, one-handed bank shot with 1:49 left but was whistled for an offensive foul.

The play was reviewed and the call stood. Boston kept its 112-111 lead with 1:49 left in OT.

Embiid, the NBA MVP, kept his composure and eventually got to the line to sink two free throws with 59 seconds left.

Embiid had 34 points and 13 rebounds. Harden added nine assists and eight rebounds.

Tatum struggled to score early but finished with 24 points, 18 rebounds, six assists and four blocks. Jaylen Brown scored 23 points and Smart had 21.

They went to overtime tied 107-all after Smart was short on a 3 at the horn on one of the few clutch shots Boston missed in the fourth quarter.

Boston’s fun began in the period when Smart and Brown buried consecutive 3-pointers and Tatum attacked the rim for a bucket that wiped out an eight-point hole in 90 seconds.