Justin Thomas followed his opening-round 61 with a two-under-par 69 on Friday to maintain the lead at the RBC Heritage in Hilton Head Island.
Thomas' steady round featured four birdies and two bogeys, pushing him to 12-under for the event after he tied the Harbour Town Golf Links course record on Thursday.
The two-time major champion is seeking his first victory since the 2022 PGA Championship.
Shane Lowry shot another under-par round; however, he lost further ground on the leader as his one-under par 70 leaves him eight shots behind Thomas at the half-way stage.
Lowry shot a three-under 68 on Thursday and sits in a share of 31st place going into the weekend.
The Offaly man opened and closed with bogeys, but birdies at the fifth, ninth and 14th ensured he was under par for the day.
Si Woo Kim of South Korea fired the round of the day, a seven-under 64, to leap into a share of second place at 10 under with Russell Henley.
American Andrew Novak and England's Tommy Fleetwood are tied for fourth on nine under, while Scottie Scheffler settled for a one-under 70, including all pars on the back nine, and is tied for sixth on eight under with Canadian Mackenzie Hughes.
There is no 36-hole cut at the $20 million signature event.
