Andres Romero took control of the Reno-Taho Open with 15 points in the second round as Padraig Harrington stagnates at the Montreux Golf and Country Club.
The $3million tournament is the only one on the PGA Tour to use a Modified Stableford format which allocates points based on the number of strokes taken at each hole.
Eight points are awarded for an albatross, five for an eagle, two for a birdie, zero for a par, minus one for a bogey and minus three for a double bogey or worse.
Romero had nine birdies, a bogey and a double bogey, giving the Argentinian a three-shot advantage over Australian duo Stuart Appleby and Rod Pampling and South Korea's Charlie Wi.
Three-time major winner Padraig Harrington failed to make much progress, with four birdies and two double bogeys leaving him 20 shots off the pace.
The Dubliner faces an important two weeks as he tries to secure his FedEx Cup play-off place. He currently lies 123rd in the standings with the top 125 to qualify after next week's US PGA Championship.
Pampling's was the round of the day, nine birdies and one bogey giving him a 17 which moved him into contention, while Wi's was blemish-free and included five birdies and an eagle on the par-five 13th.
Overnight leader Josh Teater slipped out of contention as he failed to follow his exceptional opening round.
The American broke even and lies seven shots off the pace after a round of three birdies, three bogeys and a double bogey.