The 30-year-old carded six birdies and an eagle on his way to a second round of 63 and sits three clear at the halfway point of the Sony Open on 13-under.
Zach Johnson is part of a five-way tie for second on 10-under while Justin Thomas is seven off the pace on six-under.
It looks like Harman's tournament to lose and he clearly feels he has a point to prove after missing last year's Presidents Cup as Steve Stricker instead selected Phil Mickelson due to his experience.
Harman has recorded top-10s in his four tournaments since and says the frustration of being overlooked for a place at Liberty National is spurring him on at Waialae Country Club.
"Missing out on the Presidents Cup hurt. I didn't feel like I deserved a pick by any means, and I would've been happy with one, but I didn't feel like I played well enough to make it where it was a snub by any means," Harman said on Friday.
"But I'm definitely motivated by that. I was really disappointed with the way I finished the year and the Playoffs because I wanted very badly to make that team and I didn't get it done."