Anthony Kim powered to the top of the leaderboard at the Honda Classic on a good day for low scoring at Palm Beach Gardens, Florida.
Kim carded a six-under-par 64 in his second round, equalling the course record, and shared the lead at eight-under with Camilo Villegas of Colombia.
Villegas went round in his second successive 66, as two of the brightest emerging stars on the PGA Tour - Villegas is 28 and Kim is 24 - led from one of its most senior players.
Fijian Vijay Singh, 47, is chasing his first win since 2008 and strengthened his chances with a round of 66 to follow his opening 67.
Kim's fellow American Jerry Kelly stood in fourth place on six under after a round of 65, and overnight leader Nathan Green dropped back into a share of fifth place on five under after a level-par 70.
Alongside Green in a group of five were former Masters champion Mike Weir and Ireland's Graeme McDowell after rounds of 64 and 67 respectively.
Two other players shot 64 - Canadian Stephen Ames and England's Paul Casey - and they both shot up into a share of 12th place.
Co-leader Kim was pleased with his round, after struggling in terms of scoring in the early weeks of the season.
He said: "I feel really good. I've been working hard on my game, and the last couple of months I've really started to play better. I haven't put four good rounds together. I'm happy to have another opportunity to putt four good ones together and hopefully have a chance to win the tournament on the back nine.
"I haven't even been thinking about what I'm going to shoot. I didn't have a goal, a number in mind, but just to go out there and hit some quality golf shots, it's been a long time since I've been able to have confidence and fire at some flags and be able to be aggressive and feel comfortable in that situation.
"So I'm really happy with how I'm playing. It's just a matter of time before I put four good ones together and start winning some golf tournaments again."
Singh made a monster birdie putt at the 17th, and savoured the moment.
He said: "I was just trying to get close. I had a good line and it wasn't going to break too much and I hit a good putt. The pace was good, and it looked good all the way but I didn't want to jump up and down before it went in."
Further down the field there was disappointment for England's Oliver Wilson, who followed his opening 66 with a 73 to plummet down into a share of 23rd place.
Ireland's Rory McIlroy moved to level par after a one-under 69, while Lee Westwood's 71 left him on the same mark.
Justin Rose and Padraig Harrington had rounds of 72 and 71, respectively, to be two-over, while Sergio Garcia made the cut by just one shot after recovering well from his first-round 74 by going round in 69.
England's Greg Owen will have a free weekend though, after a 73 left him five-over.
American Steve Flesch joined Owen in missing the cut, but the 42-year-old at least produced a gutsy 66 after yesterday's dismal 78 to progress to four-over.