KJ Choi surged into a two-shot lead at the AT&T National with a six-under-par 64 on Friday.
The South Korean, winner of this tournament in 2007, carded the best round of the second day, and an Aronomink Golf Club course record, to head into the weekend ahead of Chris Riley, Charlie Wi, Justin Leonard and Bo Van Pelt.
Choi started slowly and bogeyed the par-four 11th as a record round did not appear to be on the cards. But he turned his day around with back-to-back birdies at the par-four 15th and par-five 16th, and the 41-year-old then reeled off four successive birdies between the par-four fourth and par-four seventh. Another birdie at the par-five ninth ensured he would reach the halfway stage on seven-under.
Riley, Wi and Van Pelt all shot four-under-par 66s to join Leonard, who shot 67, on five-under-par, with Charles Howell III (68), Bryce Molder (67), Jeff Overton (65) and Kyle Stanley (69) a shot further back.
Joint overnight leaders Adam Scott and Hunter Haas both slipped down the leaderboard following disappointing second rounds that saw them fail to break par. Australian Scott shot two bogeys and one double-bogey to wipe out his three birdies as he shot a one-over-par 71, while American Haas also shot two bogeys and a double-bogey in a four-over-par 74.
Defending champion Justin Rose managed to make the cut despite following a par-70 first round with a two-over-par second, but on two-over he faces a huge task to get back into the reckoning on Saturday.
