Greg Norman continued to go well but American amateur Tim Jackson upstaged a who's who of former Major champions and tour winners to take the halfway lead at the US Senior Open at Carmel, Indiana.
The 50 year old former Walker Cup player from Tennessee, with his 15 year old son Austin caddying, shot a five under par 67 at Crooked Stick to complete the first two rounds in 11 under par.
That put him one stroke clear of second placed Joey Sindelar, two ahead of Fred Funk and three shots in front of Norman.
"Well, it is rare, but I'm enjoying it," Jackson said of his position in a championship which has never had an amateur winner.
"These last two days have been the best for me. I mean, just sinking into the fact that I made the cut, I think I made the cut, so that's one goal accomplished for the week."
Jackson had shared the first round lead with Sindelar, Dan Forsman and Norman, each having shot opening 66s.
Yet the amateur's second round 67 eclipsed his rivals, Sindelar shooting a 68, Funk moving into contention with a 67, Norman shooting 70 and Forsman taking fifth place with a 71.
Jackson, though, is expecting the competition to hot up some more in the third round.
He explained: "Tomorrow is going to be a different animal, I'm sure. I'm playing toward the end tee times, and the hardest thing is killing time ahead of that and trying to get your mind off of it and not be too stressed out.
"I'm going to be nervous, I know that. I just have to keep focused on my routine and literally, I know this is cliche, but just one shot at a time."
Norman was relieved to get off the course after a round of five birdies and three bogeys.
The Australian said: "It was a long day. That might have been the longest day on the golf course I've had in a long time. It was hard work out there, tough pins.
"The greens were tough speed to get figured out and my yardage always seemed like they were right in between clubs, I couldn't go at a hard shot. It was an awkward day."
Last week's Senior Open Championship presented by MasterCard winner Loren Roberts kept in touch with the leaders with a 71 that left him at five under while recent Open Championship runner-up Tom Watson carded a 72 to reach halfway at one under par in a tie for 26th alongside defending champion Eduardo Romero of Argentina.
Bernhard Langer shot a 71 to leave him at level par for the tournament while Ian Woosnam will also start the third round at even following a second 72 in succession.