Around 8.15 pm local time Phil Mickelson, who had finished his first round 16 hours earlier, rolled in a 25 foot birdie putt at the final hole to join Billy Horschel in the lead at 1 under par.
The pair are one ahead of five players at even par, namely Luke Donald, Steve Stricker, Justin Rose, Ian Poulter and Chinese Taipei youngster Pan, Cheng-Tsung with both Poulter and Pan required tor return to the golf course on Saturday morning to complete their second rounds.
Pan still has nine holes to play while Poulter will return to the 15th hole to complete his round so both have opportunities to join or perhaps even pass the leaders tomorrow morning.
At 1 over and having completed their rounds are John Senden and Nicols Colsaerts while also one the same score and still some holes to play are Jerry Kelly, Charley Hoffman and US Open debutant Michael Kim.
It was an intriguing day as Merion continued to bare her teeth despite the relatively benign conditions that have prevailed over the opening two days.
When play was called early on day one 15 players were under par but when the opening round was completed early on day two only five players were under par.
Now only two are guaranteed to be under par at the completion of 36 holes although things might change tomorrow morning.
For Horschel it has been a stunning display of US Open style golf, hitting 31 of 36 greens in his opening 36 holes and all 18 today. A breakthrough PGA Tour winner in New Orleans earlier this season, Horschel has begun to shine on the PGA Tour after much of his first couple of years were plagued by injury issues. This is his second US Open having missed the cut as an amateur when on debut in 2006.
Horschel has struggled with limiting distractions on the golf course and it is one thing he and his sports psychologist Fran Pirozzolo have worked on over the past year.
"I've acquired some patience, not as much as I wish I had. But I just think that the older I get, the more mature I get on the golf course, the more understanding that if I do have a bad stretch of holes, It's not that I don't hit the panic button, I just don't press right away. You're going to have a couple of bad holes, but if you get in a flow you can sort of get something going.
"But the patience is something that has always been a struggle for me. I'm doing a really good job of it this week, staying patient and just taking what's in front of me. I'm trying to keep a smile on my face and be happy with anything I do. If I can execute every shot, that's all I can try to do out there this week."
Mickelson's final hole birdie might assist in overcoming a day where his play generally was very good although he was unable to convert several very good opportunities early. The putt on the last has given him momentum to carry over to Saturday's third round and he still appears a good chance to overcome his US Open lockout.
"I got shut out today," said Mickelson. "I played really well. Even though I shot 2 over, it was the birdie opportunities that I didn't capitalize on. Had I made one on 2 or that birdie on 8 or 9 or 11, I would have changed kind of the momentum of the round. I played well today even though I didn't feel the score was what I thought it should be."
Mickelson and his playing partners were keen to get finished before play was halted and they ran the gauntlet to do so.
"Last night they called it at 8:19, so it was going to be close. We told DJ and his caddie Keith Sbarbaro, (who were in the group ahead) we may hit one shot and they looked out for it. So they moved to the side, Keegan hit, and that means the rest of the group can finish. It worked out we were fine time-wise, but it's nice when guys like that help out, and it was good."
Amateur, Pan, has been the surprise although many who have seen him play swear that he is a future star of Asian golf. A University of Washington attendee, Pan has finished runner-up at each of the last two Asia Pacific Amateur Championships and has an impressive collegiate record.
John Senden is at 1 over and leads the Australians in a share of 8th position. Senden was the leading Australian at Olympic Club last year and appears to be converting his US Open style game into results.
Interestingly however he has been well down in greens in regulation to date this week although has the second most birdies to date over the opening 36 holes suggesting an improvement in his putting. He has recorded the second most birdies for the opening 36 holes (8) behind Luke Donald.
Mathew Goggin has done well to stabilised his round after dropping four shots in his first nine holes. he finished with 74 to be at 2 over and in a share of 13th.
Jason Day still has four holes to play to hopefully improve on what had been a tough day. A birdie late in his round will help, the 2011 runner-up only four behind the leader at present.
Given Geoff Ogilvy's recent struggles, he too has done well to comfortably make the cut at 4 over while Adam Scott at 7 over will make the cut, Alistair Presnell at 8 over likely to do the same and Aaron Baddeley still on the golf course at 8 over still with some work to do if he wants to play the third round.
The effort of Scott was a big surprise. He returned to the course early on Friday to complete round one and dropped five shots in his last seven holes. He kept in touch with the leaders until a run of four consecutive bogeys in the later stages of his second round saw him drop to 7 over and when he finished his round there was some concern that his place in the weekend field was in jeapordy. As the afternoon progressed however it became clear he would make the cut and although not finalised he appears safe in that regard. He is currently in 53rd position at 7 over and eight shots from the lead.
Nearly 70 players completed their second rounds leaving just under half of the field still to complete round two.
The Championship is expected to get back on schedule by Saturday afternoon and with good weather forecast for the final two rounds then the event will finish on schedule on Sunday evening.