Luke Donald is on course to become world number one after a second-round of 65 moved him into a one-shot lead at The Heritage at Hilton Head.
The Englishman had opened with a four-under 67 on Thursday, and followed it up on Friday with five birdies on the front nine and two more at 11 and 15 to move a stroke clear of first-round leader Garrett Willis on 10 under par.
A win in south Carolina will see Donald climb two places and top the world rankings - with current leader Martin Kaymer having a week off and Lee Westwood playing in a tournament worth fewer ranking points in Indonesia - and the 33-year-old said of his impressive performance: "It was a solid day. I got off to a great start, again, birdieing the first two holes gave me some good momentum. I played that front nine really well.
"The back nine is a little bit tougher, but, again, I did a lot of good things today, drove it reasonably well. Some of my misses were in good places where I could get a good up-and-down."
Willis, whose decision to continue with his conventional putter instead of switching to a belly putter yielded a seven-under 65 on the opening day, could not keep up his high standards as he started the front and back nines with bogeys in a round of 69, but he remains in the fight for victory.
Camilo Villegas was three under on the day as the Colombian moved into a tie for third while Jim Furyk and Masters contender Jason Day were two of the big movers on the day as they also moved to eight under with five-under and six-under rounds respectively.
Ian Poulter is a shot further back after a flawless round of 66, with Northern Ireland's Graeme McDowell at two under following his 69.
But Poulter and McDowell's Ryder Cup team-mate Francesco Molinari missed the cut after the Italian posted a three-under-par 74 to leave him four over overall.