Dustin Johnson's U.S. Open advantage grew to four shots with overnight co-leader Ian Poulter reaching the turn at one over par, as Phil Mickelson, Jordan Spieth and Rory McIlroy flirted with the cut.
World number one Johnson carded a three-under 67 despite tough conditions at Shinnecock Hills to return to the clubhouse leading by three strokes, but Poulter's opening bogey moved him back to even par for the competition and increased the gap to the 2016 champion on four under.
In the marquee group, Mickelson and Spieth were one shot within the projected cut line of nine over, though there remained scope for movement with skies clearing.
Spieth was at even par for his round through eight, while Mickelson was one over. McIlroy needed to gain shots after an opening 80, but he bogeyed the second and the seventh to slip to 12 over for the championship.
Poulter started at the 10th and narrowly missed a 37-foot putt to save par, but he kept his cool and made the turn in a share of second at even par overall.
Spieth countered a bogey at the par-four third with a gain on the fifth, while Mickelson, who dropped shots at the first and third, was two feet away from successive birdies at the sixth.
Justin Rose was at even par through 10 and joining him in a six-way share for fourth was Paul Casey, who was two under through nine.