Matt Fitzpatrick leads by a stroke from Ryder Cup teammate Viktor Hovland at the RBC Heritage after a blemish-free round of 63.
The 2022 US Open champion racked up eight birdies at the Harbour Town Links, with three in a row coming on either nine as he reached the midway point at 14 under par.
He sat on a three-stroke lead in the clubhouse throughout most of the afternoon wave, until a late surge from Hovland, saw him draw up to within one stroke.
The Norwegian, whose last PGA Tour win came at the Valspar Championship 13 months ago, carded a second round 65, with five birdies on the front nine, and two more coming on the 16th and 17th.
Harris English occupies third spot on his own on 10 under par, three strokes further back. Ludvig Aberg, Patrick Cantlay and Sepp Straka share fourth spot on nine under.
Shane Lowry is in a tie for 40th on three-under par after a second round of 69.
Lowry, who was upfront about his disappointment following his fourth round collapse when in contention at Augusta last week, registered three birdies on Friday.
The first two came on both par-5s on the front nine, with another coming on the 11th hole. He dropped a shot on the 14th after hitting his tee shot into the lake on the right at the par-3.
