The 33-year-old needs to win at Hilton Head Island to usurp Martin Kaymer at the top of the standings and he is in perfect position to do so after adding a six-under par 65 to his opening round 67 to sit one shot clear of first-round leader Garrett Willis on 10-under par.
The Hemel Hempstead-born star carded seven birdies and just one bogey on Friday to move up to the top of the leaderboard and he could become the third European in a row to hold the title of world number one after Lee Westwood and Germany's Kaymer.
But there are plenty of top-class players in contention with Willis just a shot back on -9, while Jim Furyk and Camilo Villegas are in a group of four players on -8
Ian Poulter's second-round 66 has propelled him up to -7 and a share of seventh place with US star Ben Crane, while Australia's Nick O'Hern was another big mover on day two and shot a 66 to move to six-under for his first 36 holes.
Graeme McDowell has struggled with consistency of late and he laboured to a two-under par 69 on Friday but remains in contention at -5, while the man who came so close to winning last year, Brian Davis, sneaked into the weekend with a disappointing three-over par 74 to sit right on the cut line at even par.