Sweden's Kalle Brink birdied two of the last four holes to go two strokes clear with a round left of the Challenge de Sable in France.
It enabled the 23-year-old from Helsingborg to card a 67 for 204, 12 under par, two better than Carl Suneson of Spain, who shot a best-of-the-day 66, and Austria's Markus Brier, who had a 68.
Suneson, who won the Challenge de Espana at El Saler four weeks ago, set the clubhouse target after running up seven birdies in his 66. With four holes to play Brink had also got to 10 under but he then birdied the 15th and 16th, both par-fours, to take over at the top.
It was a different story for Lucas Parsons, who led by three overnight. On a windy day with the greens becoming hard, conditions were tricky and he suffered with five bogeys in his 73, which leaves the Australian in joint fourth place on 207.
Parsons was also on 10 under with five to play but, unlike Brink, he slipped back, dropping shots at the 16th and 17th before a birdie-four at the last left him on nine under.
On the same mark are the French duo of Pascal Edmond, amateur Julian Van Hauwe, and Euan Little from Scotland. Edmond had a 69 but Van Hauwe returned 67, which included an inward 32 with four birdies in a row from the 11th.
Little, still seeking his maiden Challenge Tour victory, is showing a welcome return to form. He was out in 34 with a trio of birdies, while he added a fourth coming home, rounding off a fine round with an eagle-three at the last.
England's Scott Watson, who a year ago lost a playoff for the Challenge de France over the same course, is among a group in joint 10th place on 209 after a 71. On the same mark is Mark Litton after a 67, and fellow Welshman David Park, current leader of the ranking, who was again the epitome of consistency with 69.