Campbell closed a 4-under-par 67 Saturday with a birdie at the par-4 18th hole, while Piercy, a PGA Tour rookie, shot 6-under 65 and watched from the clubhouse when Campbell joined him at 17-under 196 and a joint one-stroke lead at the Tournament Players Course Summerlin.
Martin Laird, also a PGA Tour rookie, shot 4-under 67 Saturday, and at 16-under 197, is alone in third place.
Jason Bohn (65), Jeff Klauk (66), Bob Heintz (68) and 2007 champion George McNeill (63) all are 15-under 198 and share fourth place.
"My legs have been weak all week," a nervous Piercy said. "It's been good overall -- just taking it one shot at a time, which is the whole thing."