James Hahn shot a bogey-free six-under 65 to take an outright lead after the second round of the Waste Management Phoenix Open was suspended on Friday.
Rickie Fowler, Shane Lowry and Hideki Matsuyama held the joint lead overnight, with Hahn two strokes behind, but the American hit back on TPC Scottsdale's Stadium Course.
Hahn, who won his first and only PGA Tour title last February at the Northern Trust Open, went off at the 10th tee and holed a birdie from 19 yards to kick things off.
The 34-year-old sunk five more birdies, as well as securing crucial pars on holes 16 and 17, to sit at 10 under.
Fowler dropped down to joint second after round two alongside New Zealander Danny Lee.
The American birdied his final hole for a 68, while Lee finished with a 66.
Lowry and Matsuyama sit equal fourth after managing scores of one under par, while Harris English joins them after his four under.
Three-time Phoenix Open winner Phil Mickelson managed just an even-par round which saw him drop down to tied for 37th, while defending champion Brooks Koepka carded a 72 to move down to joint 21st.
An estimated 160,415 fans were in attendance for the second round, which broke the Friday record of 123,674 set in 2014.
It was also the 10th-largest figure for any day in tournament history.