Campbell had four consecutive birdies in one stretch of the second round for a 6-under-par 64, matching the record-tying score by Javier Colomo in Thursday's opening round.
Campbell is at 9-under 131 after 36 holes. That's one stroke better than Fredrik Andersson Hed, Miguel Angel Jimenez and Zhang Lian-wei, who are tied at 8-under. Andres Hansen, who also tied the course record Friday, is in fifth at 7-under. The top five players are all at least 40 years old.
Colomo staggered to a 1-over 71 and is tied for sixth at 5-under. Defending champion and world No. 1 Rory McIlroy four-putted his final hole and missed the cut.
Andersson Hed, who had three bogeys in a four-hole span, and Zhang each shot 66 in the second round and Jimenez turned in a bogey-free 3-under 67.
Campbell opened his second round with a birdie but then had a 4 at the par-3 second hole. A birdie at No. 3 -- a par-5 he eagled Thursday -- got him back in red numbers. A run of birdies over Nos. 7-10 and a closing birdie gave Campbell the outright lead.