Luke Donald, a four-time runner up in the US PGA Tour's Heritage, pitched in for a birdie at 18 on Friday to seize a share of the halfway lead alongside Graham DeLaet.
England's Donald hit just 11 of 18 greens in regulation. But his five birdies included three in a row at the fourth, fifth and sixth.
He followed his only bogey of the day at 11 with a birdie, and holed out at the last for a 67 and a 10-under par total of 132.
"Obviously wasn't a great second shot, bounded out to the right," he said of his approach at 18. "But the grass is really nice so you can really get it to nip and just played it perfectly. It was a little bit of a struggle today, but my short game helped me out."
Donald, a five-time winner on the US tour, has six top-three finishes at Harbour Town Golf Links, most recently claiming a share of second last year.
Canada's DeLaet, seeking his first tour title in his seventh season, followed up his first-round 65 with a 67 that included an eagle at the par-four ninth.
"I holed a wedge," said DeLaet, who had 109 yards to the hole from the right fairway. "It was a perfect shot, but there's obviously some luck involved in that."
Despite a bogey at the third, DeLaet delivered a crisp performance, hitting 15 greens in regulation. He got going with a birdie at the eighth, and after his eagle had a birdie chance at 10 before picking up shots with birdies at 11 and 12.
DeLaet and Donald were two strokes in front of England's Ian Poulter and American Webb Simpson, who both shot 68.
Poulter, playing on a major medical exemption, has this week and one more start to collect the prize money he needs to secure his playing status for the rest of the season.
Since returning from a foot injury in October Poulter has made eight starts on the US tour, making five cuts.
Overnight leader Bud Cauley carded a 72 that included a double-bogey seven at the 15th to fall into a group three shots off the lead on 135.
He was joined by fellow Americans Pat Perez (67), Jason Dufner (67) and Sam Saunders (70) and Canadian Nick Taylor (66).