Dustin Johnson opened up a four-shot lead during day two of the US Open as Tommy Fleetwood surged through the field with the lowest round of the week so far.
American Johnson entered the day in a tie for the lead as one of just four players under par and carded a 67 to get to four under and sit four shots ahead of Ian Poulter, who was in the very early stages of his second round.
Johnson was the only player under par as Shinnecock Hills Golf Club continued to provide a stern test but Race to Dubai champion Fleetwood showed that good scoring was possible with a brilliant 66.
That was nine shots better than his round one total and moved him to one over alongside Swede Henrik Stenson as the nearest challengers in the clubhouse.
Stenson had to fight back for the second day in a row, coming home in 32 for a level par 70 as he searches for a second Major Championship.
Johnson - the 2016 champion - regained the Number One spot in the Official World Golf Ranking on Sunday thanks to a win on the US PGA Tour and is going for back-to-back victories and his own second Major triumph on Long Island.
Joint overnight leader Russell Henley got off to a flying start, putting approaches to nine and 12 feet on the tenth and 12th to jump out to three under and a two-shot lead.
Johnson cut that gap to one with a tee-shot to nine feet on the 11th and when Henley failed to get up and down from a greenside bunker on the 14th, the lead was tied again.
The rain had been falling lightly and it got heavier as Johnson was playing the par five 16th but that was no distraction for the 33 year old, who played the hole in textbook fashion and holed an eight-footer to hit the front on his own.
Henley then got in huge trouble on the third, going left off the tee and playing out sideways after two failed attempts to get out of the rough stuff, eventually surrendering a triple bogey.
Johnson had got up and down from sand on the 17th and 18th but he could not repeat the trick on the first as he dropped a shot to see his lead cut to one.
A 16-footer on the fourth moved him back to two ahead and when he holed a brilliant 45-foot putt on the seventh, he was the first man this week to get to four under.
That gave him a three-shot lead over Poulter but the Englishman made a bogey in the opening two holes of his second round.
Englishman Fleetwood put his approach to six feet on the tenth but gave the shot straight back after finding sand before holing from five feet on the 13th to turn in 34.
A brilliant 40-footer on the second kick-started his back nine and after a three-putt on the fourth he played the par five fifth in textbook fashion, put his tee-shot to 13 feet on the seventh and holed a 25-foot putt on the ninth.
Stenson was four over after five holes on Thursday and left himself with another mountain to climb in round two after making bogeys on the second, sixth and seventh.
An 18-foot putt on the 13th gave the 2016 Open Championship winner a foothold and he hit a brilliant second to 20 feet on the 16th to set up an eagle.
Henley had bounced back with a birdie on the fifth but dropped shots on the seventh and ninth to be the only man in the clubhouse at two over.
Spaniard Rafa Cabrera Bello and Swede Alex Noren were eight shots off the lead.
