Phil Mickelson maintained a four-stroke lead at the Phoenix Open on Friday, despite denting an otherwise strong second round with a double bogey at the 18th hole.
Mickelson, who missed shooting golf's magic number of 59 in the first round by only one shot, followed up with a six-under 65 for a 17-under total of 125.
His stumble at the finish, however, meant he missed out on the US PGA Tour's 36-hole scoring record.
Although he was disappointed to drop two shots at the TPC Scottsdale's par-four finishing hole -- where he hit his tee shot into the water -- Mickelson said the wobble could help him in the long run.
"It's very possible that's going to help me because it's got me refocused, that I cannot ease up on a single shot," said Mickelson, who failed to reach the green with his approach at 18 and would have needed to hole out for the record.
Instead he watched his chip go past the cup, then two-putted.
His second round included six birdies and an eagle at the par-five 15th and left him four strokes in front of Bill Haas.
"These guys are going to make a lot of birdies and I've got to get after it and cannot make those kinds of mistakes," Mickelson said as he looked forward to a weekend that he predicted would be a "shootout".
Mickelson, a two-time winner of this event, didn't pick up his first birdie of the day until the seventh. He added another at nine, then reeled off a string of three birdies starting at the 11th hole.
At 15, his approach from the fairway landed within four feet and he made the eagle putt. He drove the green on the par-four 17th en route to a birdie.
Mickelson was one stroke off the US tour's record for 36 holes of 124, set by Pat Perez at the 2009 Bob Hope Classic and matched by David Toms at the 2011 Colonial.
Haas carded a seven-under 64 that included seven birdies for 129.
Keegan Bradley had seven birdies and an eagle in an eight-under 63 that put him on 130, tied with Brandt Snedeker who posted a 66.
Bradley's round matched his career best on the PGA Tour.
Argentina's Angel Cabrera (65), South Korea's Charlie Wi (63) and Humana Challenge winner Brian Gay (66) were tied on 131.