Padraig Harrington plays his tee shot on the 10th hole during the second round at the 2013 U.S. Open at Merion Golf Club in Ardmore, Pa. on Friday, June 14, 2013. (Copyright USGA/Michael Cohen) Pádraig Harrington putting woes continue to haunt him.

Having hauled himself into contention for a tilt at the US Open, Ireland’s three-time major winner frustratingly undid all his hard work with a late double bogey six in the gathering gloom at a punishing Merion last night.

The Dubliner started the day six shots behind pacesetter Phil Mickelson on three over par before cruising to within two strokes of surprise clubhouse leader Billy Horschel when he picked up birdies at the seventh and eighth in the delayed second round.

A three-putt bogey at the 11th dropped him back to two over par and after missing a 15 foot birdie chance at the short 13th and then saving par from eight feet after a poor first putt at the 14th, he double bogeyed the 15th in fading light to end the day five shots behind Horschel and Mickelson, who birdied the last for a 72, in joint 23rd place on four over par.

Harrington’s drive at the 15th flew into heavy rough on the right but he got a flyer with his second and ended up in an unplayable spot under a tree, just two yards from the out of bounds markers.

Padraig Harrington on the 12th hole during the second round at the 2013 U.S. Open at Merion Golf Club in Ardmore, Pa. on Friday, June 14, 2013. (Copyright USGA/Michael Cohen)Unable to get a clear swing at the ball, he opted to take a penalty drop but after hitting a magnificent downhill pitch that burned the edge of the hole, finishing four he opted to putt out after the hooter sounded to suspend play.

Just as happened to Rory McIlroy on Thursday evening, it proved to be the wrong decision and he made a tentative stroke with his newly acquired belly putter, missing his slippery four-foot bogey putt comfortably on the low side.

Shoulders slumped, the Dubliner was left to reflect on what might have been having also missed a two foot birdie putt at the fourth. [Correction - Harrington had found a cross bunker at the fourth but hit a great fourth shot to two feet and tapped in for par]. But despite his poor finish, he is still well in contention with fives shots covering the top 32 on the leaderboard.

Play will resume at 7.15am on Saturday with 68 players still to complete their second rounds.

They include Waterford Castle’s Kevin Phelan, who failed to reproduce the brilliance of his opening 71 as he followed bogeys at the third, fifth and sixth with a double bogey five at the ninth to slip dangerously close to the projected cut mark on six over.

The axe for the top 60 and ties is expected to fall at eight over par with Phelan tied for 43rd with the tough back nine still to negotiate this morning.

Billy Horschel reacts to a missed birdie on the 17th hole during the second round at the 2013 U.S. Open at Merion Golf Club in Ardmore, Pa. on Friday, June 14, 2013. (Copyright USGA/Hunter Martin)However, there will be no early morning wake up call for Mickelson, whose craftily beat the hooter and birdied the 18th for a scrambling 72 to join Horschel in a share of the lead on one under par.

“Last night they called play at 8:19, so it was going to be close,” Mickelson said.  “We told DJ [Dustin Johnson] and his caddie Keith Sbarbaro, we may hit one shot and they looked out for it.

“So they moved to the side, Keegan [Bradley] 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.”

The birdie put a gloss on a tough second round for the left-hander who followed a three-putt bogey at the first with bogeys at the 12th and 13th to fall back to level par before that closing birdie allowed him to finish in a share of the lead.

“I got shut out today,” said Mickelson, who has five runner up finishes but no wins in the US Open.  

“I played really well. Even though I shot two‑over, it was the birdie opportunities that I didn’t capitalise on. It feels good being in contention heading into the weekend.”

Phil Mickelson plays his second shot on the 10th hole from the rough during the second round at the 2013 U.S. Open at Merion Golf Club in Ardmore, Pa. on Friday, June 14, 2013. (Copyright USGA/Darren Carroll) Mickelson and Horschel were the only players in red figures at the end of another 13-hour day.

World No 50 Horschel, who won his first PGA Tour event in New Orleans earlier this season, set the pace on one under par when he hit 17 greens and one fringe en route to a 67 that equalled Mickelson for the low round of the week.

The 26-year old Floridian, who drew the wrath of McIlroy for his over-enthusiasm in the United States’ 2007 Walker Cup win at Royal County Down, had four birdies and a bogey and surprised himself with his patience.

Famed for his short fuse, Horschel said: “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 and Horschel are one stroke clear of Luke Donald (68-72), Steve Stricker (71-69) and Justin Rose (71-69) with Ian Poulter (14 holes) and Chinese Taipei’s Cheng-Tsung Pan (9 holes) also on even par.

Australia’s John Senden (70-71) and Belgian Ryder Cup star Nicolas Colsaerts (69-72) are just three behind on two over with Rory McIlroy and Tiger Woods lurking in share of 17th on three over after adding 70s to their opening 73s.

Ulstermen Graeme McDowell and Darren Clarke will miss the halfway cut.

McDowell had seven double bogeys in rounds of 76 and 77 to finish on 13 over with Clarke two shots further back after adding a 75 to his first round 80.