Lahiri had turned in a fine four-under 67 in the first round. The Indian ace, who is returning to the course after the Arnold Palmer Invitational, is five places down from his first round T-11th.
Lahiri is five shots behind co-leaders Canadian Graham Delaet and Luke Donald, who has been second here four times but never won the title. Both shot 67 each after identical 65s in the opening round.
Ian Poulter (66-68) and Webb Simpson (66-68) are tied third while first round leader Bud Cauley (63-72) is Tied-fifth with four others. Lahiri birdied the second and the 11th and dropped his only bogey on 14th.
In the ongoing season, Lahiri has one Top-3 (CIMB Classic T-3) and two other Top-15 finishes at Honda Classic (T-11) and RSM Classic (T-13) and is currently 60th in the FedEx Cup rankings.
However, Lahiri is aiming for some good finishes to get back to Top-50, up from his current 80th, and also wants to qualify for the President's Cup later this year.
Delaet followed up his career-best six-under 65 in the first round with a 67 to share the lead with Luke Donald midway through the RBC Heritage. Donald has finished second or third in six of his past eight visits to the RBC Heritage -- and put himself in position for another stellar finish this time, too.
Poulter, playing on a major medical extension, is on the clock to keep his card and needs about USD 145,000 in his next two events to maintain his playing status and is off to a strong start.
His 66-68 is the just the second time in seven career visits to Harbour Town he's opened with two sub-70 rounds. First-round leader Bud Cauley followed his 63 with a 72 and was in a group of five at seven-under that included former PGA Championship winner Jason Dufner and Sam Saunders, the grandson of golf's late king, Arnold Palmer.
There were 74 golfers who made the cut which came at one-under par, the lowest ever at Harbour Town. Those going home included Jim Furyk, Ernie Els, 2016 Masters champion Danny Willett and Charley Hoffman, who contended at Augusta National for much of the week before falling off the pace.