Northern Ireland's Rory McIlroy fired a two-under-par 68 to move up the leaderboard to one under after two rounds of the US Open at Pinehurst.
The 2011 champion started with a bogey at the 10th but birdies at the 14th, third and fifth holes saw him recover as low scores proved hard to come by.
Graeme McDowell dropped back to two over following a disappointing 74.
Martin Kaymer is six shots clear of the field on 10 under but Darren Clarke and Shane Lowry missed the halfway cut.
2011 Open champion Clarke endured a difficult first day to post a 75, but signed for an improved 72 on Friday.
He began his round with a double bogey seven at the 10th and three birdies and three bogeys followed in the remainder of his round.
Lowry shot a second successive 73 to lie six over and his second round included three birdies, four bogeys and a double bogey.
In contrast to playing partner and compatriot McIlroy, McDowell began his second round brightly with a birdie four at the 10th.
The Portrush man had started the day in a share for second place but bogeys at the par-four 11th and 16th holes and a double bogey six at the 18th saw his challenge recede.
McDowell, winner of the tournament in 2010, then missed a short putt for a par at the first, but a birdie at the third and a long putt for a par at the sixth boosted his fortunes, before another bogey at the fifth.
Kaymer pulled away thanks to a second 65 in a row, his halfway total of 130 eclipsing the previous championship best of 131 set by McIlroy three years ago.
The German's form has evoked memories of the Northern Irishman's record-breaking victory at Congressional when McIlroy, now 25, posted a final total of 16 under, the lowest in the history of the championship.
He was also the first player ever to get to double digits under par after the first two rounds.
American Brendon Todd is Kaymer's nearest challenger on four under, six shots in arrears of the leader.