Phil Mickelson was closing in on a fifth win at the AT&T Pebble Beach Pro-Am in California when play was suspended due to darkness.
The American, who started the final round at Pebble Beach three shots back, ended with a three-shot lead with two holes left to play.
After a rain-delayed start, Mickelson had produced a blemish-free round and holed six birdies to move to 18 under before play was called off.
Third-round leader Paul Casey, who mixed two bogeys with two birdies, was at 15 under with three holes remaining, tied with Scott Stallings who finished with a 66.
Mickelson appeared unhappy about the decision to suspend play, insisting he could "see fine" as the cameras caught him shaking his head when the news was announced.
"I totally get where (Casey) is coming from," he said in quotes on pgatour.com.
"In all honesty, it's probably a good thing because now we'll play the last couple of holes in pure conditions and it will be helpful for both of us."
Casey added: "The guy on the hot streak wants to keep going. The guy who's not, (thinks) 'let's stop'."
Australian Jason Day and Si Woo Kim, of South Korea, were in the clubhouse on 13 under.
Scot Russell Knox closed at nine under after a fourth-round level-par 72, one shot clear of Northern Irishman Graeme McDowell.
Play will resume at 8am (4pm Irish Time) today.