Julien Guerrier carded a five-under-par 66 on day two of the Portugal Masters to open up a commanding five-shot lead at the halfway point in Vilamoura.
The 35-year-old is hoping to claim his first win on the European Tour and went into Friday's play a shot off overnight leader Liam Johnston after a bogey-free opening round of 62.
But as Johnston went backwards, Frenchman Guerrier produced another high-quality round, albeit not entirely flawless.
He made his first bogey of the tournament on the opening hole of the second round but then recovered with three birdies in the next four holes.
After taking over at the top of the leaderboard, Guerrier bounced back from another bogey on the sixth with pars on the next three holes at the Dom Pedro Victoria Course.
And he further increased his lead on the back nine thanks to four more birdies.
"I'm feeling great. It looks easy but it's not," Guerrier, who endured an injury-plagued 2019 season, said after reaching 14-under 128 through 36 holes.
"After shooting nine under it's always tough to make a good score so I'm really happy to have played good. I just try to hit it on the fairways and hit the greens after.
"I'm feeling good on the greens so I think it's a bit easier when you are confident around the green. In Valderrama it was really tough so that was more about fighting spirit.
"After the injury you try to get a good level and find your mark on your game under pressure so it's perfect for me to play on the weekend."
Sihwan Kim matched world number 670 Guerrier's five under for the day to move up to second place on nine under par after a hectic back nine that included three bogeys and six birdies.
Former leader Johnstone sat tied with eight others in third, the Scotsman failing to build on a sensational first round of 61 as he posted a three-over-par 74.
Antoine Rozner, Wilco Nienaber, Scott Vincent, Adrien Saddier, Adrian Meronk, Martin Simonsen, Matthew Jordan and Marcus Armitage were also seven shots off the pace.
Elsewhere, Jonathan Caldwell and Mathieu Fenasse produced holes-in-one, on the sixth and eighth respectively.
Pre-tournament favourite Tommy Fleetwood was in trouble until three birdies on the back nine meant he avoided a missed cut, yet after a level-par 71 he sat 11 shots behind Guerrier.