Bryson DeChambeau carded an eight-under-par 64 to take the lead after the second round of the Hero World Challenge at Albany Golf Club in the Bahamas.
World number seven DeChambeau started Friday's session down in 11th but climbed to the top of the standings on 11 under for the tournament with an impressive round.
The 2020 US Open winner double-bogeyed on the par-four 16th after pulling his drive into a bush, but that was the only blemish as he made 10 birdies.
DeChambeau, whose only title this calendar year came at the Arnold Palmer Invitational in March, is one stroke clear of fellow Americans Collin Morikawa, Tony Finau and Brooks Koepka.
Morikawa will overtake Jon Rahm as the world's number one should he win the tournament, and he would have had a share of the lead if not for a bogey on the 18th.
"When I put myself in the fairway, I was converting, I was making the birdies when I needed to," said Morikawa.
“I still felt like the driver's a little off, but, you know, get my timing a little bit better tomorrow and the next day and we'll be just fine."
Finau began the back nine with a bogey but recovered well with four birdies on the following eight holes to remain in strong contention for the title with two rounds to go.
Rory McIlroy, who held a share of the first-round lead with Daniel Berger and Abraham Ancer, shot a one under-par 71 on Friday to slip four off the pace.
Berger is fifth after a round of 69, while Ancer's 73 – which included five bogeys – saw him drop outside the top 10.
Meanwhile, Sam Burns impressed with seven birdies for a second-round 65 that was bettered only by DeChambeau as he climbed into a tie for sixth alongside Tyrrell Hatton.