Retief Goosen is in the frame for a second US Open Championship title after a sparkling four under par 66 took him to four under par and within two strokes of the early clubhouse lead held by Masters Champion Phil Mickelson, who also shot a 66.
European Tour Member Goosen, the 2001 US Open Champion and winner of the Volvo Order of Merit in 2001 and 2002, fired five birdies with just the one dropped shot on the 11th to surge through the field in his bid to add to his triumph at Southern Hills CC, Tulsa, three years ago.
"I like links golf and this course is obviously playing that way," the 35-year-old said.
"It plays a lot like Southern Hills with elevated tees and the greens up above. I feel very comfortable here."
The South African lies a shot ahead of another European Tour Member, Angel Cabrera. The Argentine, who was lying in a three way tie for the lead at the conclusion of the first round earlier in the day, posted a one over par 71 after a roller-coaster second round that included an eagle, two birdies, three bogeys and a double bogey.
World Number Three Vijay Singh of Fiji, who like Els has a chance of ousting Tiger Woods from the World Number One spot should he win, kept himself in the hunt with a two under par 68 to climb into the top ten.
Immelman, starting his round at one under par, picked up a hat-trick of birdies from the 11th, his second to move within touching distance of the leaders but was hit hard by a double bogey on the 18th, his ninth hole.
Two months after winning his first Major Championship by capturing the Masters Tournament at Augusta National, Mickelson was again setting the pace after adding a sparkling four under par 66 to his opening 66 to stand on six under par 134.
Indeed his 36 hole total was only one shot outside the halfway record in 104 stagings of the US Open, a record he would have equalled had his ten foot birdie putt on the last green dropped.
Mickelson recorded 17 top ten finishes on Major Championships prior to his victory in April, including fourth in the US Open the last time it was played at Shinnecock Hills in 1995.
"My swing has felt good all year - I'm swinging with confidence," he stated. "I've said in the past that I've always believed I would have had one major by the age of 34 and now that I have I really haven't felt that sense of relief.
"What I have felt is a sense of excitement and anticipation. I can't wait for the up-coming majors now because I feel I'm onto something."
Padraig Harrington of Ireland, narrowly defeated by Sergio Garcia in a play-off for the Buick Classic last weekend, added a one over par 71 to his opening 73 to lie four over for the Championship and right on the projected cut mark.