Phil Mickelson and Paul Casey shared the clubhouse lead before torrential rain forced the second round of the AT&T Pebble Beach Pro-Am to be suspended.
Mickelson looked likely to have a healthy lead at the halfway stage until he bogeyed three of his last four holes at Spyglass Hill and settled for a 68 which got him to 10 under, while Casey managed to complete a seven-under 64 on the Monterey Peninsula course before play was abandoned for the day.
Jordan Spieth is also on 10 under and had two holes of his second round to complete at Spyglass Hill when the tournament resumes on Saturday morning, the three-time major champion being one of 44 players who were still on the course when flooded greens left officials with no option but to bring the event to a halt.
Mickelson, who hit every fairway in his first round for the first time in almost 21 years, made a strong start to day two in the cool and damp conditions as he birdied the long 11th - his second - and then hit a remarkable three-wood to eight feet from the trees at the par-five 14th, although he mis-read the eagle putt and tapped in for birdie.
The four-time champion picked up further shots at 17 and 18 to turn in 32, and after missing out on another at the par-five first, he atoned with a pair of twos at the third and fifth before three wayward tee shots led to bogeys on each of the next three holes.
Mickelson did at least get one back at his final hole to close on 10 under, a score that was soon matched by 2009 US Open champion Lucas Glover when he carded an impressive 66 at Pebble Beach, while Scott Langley made it a three-way tie at the top after handing in a steady 69 at Spyglass Hill.
Three later became four when Casey completed a bogey-free 64 at Monterey Peninsula, the Englishman flying up the leaderboard when he made four birdies and one eagle in a sparkling six-hole run on the back nine, although he managed only one more gain at the sixth as conditions deteriorated.
Spieth, a four-shot winner two years ago, birdied five of his first seven holes at Spyglass Hill before the putts dried up in a run of nine straight pars, and he had just tapped in for a par-five at the long seventh when the klaxons sounded to bring the players in.
Jason Day, who was a runner-up to Ted Potter last year along with Mickelson and Dustin Johnson, was one over after 10 holes in his second round at Spyglass Hill, but the Australian then reeled off four birdies in five holes and still has three to play on Saturday morning.
But Tommy Fleetwood remains in danger of missing the 54-hole cut despite bouncing back from his disappointing, opening 73 at Monterey Peninsula - traditionally the easiest of the three-course rotation, and the Englishman was four under for day two at Spyglass with two holes to complete.
And PGA Tour debutant Ho Sung Choi is almost-certain to miss out on playing the final 18 holes at Pebble Beach after the unorthodox South Korean littered his card with five bogeys against only two birdies in a frustrating 75 which saw him slip to four over par for the tournament.