Brett Stegmaier leads heading into the final round of the Shriners Hospitals for Children Open after Morgan Hoffmann's back-nine charge faltered on the 18th.
Hoffmann was one over for the day through 12 but picked up shots on 13, 15, 16 and 17 to temporarily move a shot ahead of Stegmaier. But Hoffmann bogeyed the par-four 18th while his fellow American managed a birdie to take a one-shot lead on 13 under par.
The pair are both chasing their first PGA Tour titles, but they will be put under pressure on the final day by Kevin Na, Jimmy Walker and Chad Campbell, who are all lying on 11 under and have the experience of 10 wins between them.
Germany's Alex Cejka is a further stroke back after a terrific final three holes. The 44-year-old aced the par-three 17th and sandwiched that with birdies on 16 and 18. He is joined on 10 under by Canadian Nick Taylor and American duo Jason Bohn and Cameron Tringale to leave the top nine players separated by just three shots ahead of day four in Las Vegas.
Rickie Fowler failed to sustain his second-round charge up the leaderboard as his one-under 70 left him seven shots behind Stegmaier.
England's Greg Owen, who was a shot off the lead after day one, followed each of his three bogeys with a birdie on the next hole for a level-par 71 that leaves him 10 strokes off the pace.
Martin Laird is a shot better off after a 70 while fellow Scot Russell Knox is two strokes back on two under.
