David Lingmerth set the clubhouse target on day two of the US PGA Championship but history-chasing Jordan Spieth was hot on his heels at Whistling Straits.
The Swede was seven under after recording a second round 70 to go with his opening 67 but Spieth, who is attempting to become just the third player after Ben Hogan and Tiger Woods to win three Major Championships in a season, was just a single shot back.
Three shots off the lead sat Hiroshi Iwata who became just the 25th man to fire a record-equalling low round of 63 at a Major and broke the course record at Whistling Straits in the process.
It was a good morning for low scoring with George Coetzee firing an impressive 65 to sit two off the lead and 2013 Race to Dubai winner Henrik Stenson shooting 66 to alleviate any danger he may have had of missing the cut - which looked likely to fall around the one over par mark.
Lingmerth recorded just five pars in his round with eight birdies, four bogeys and a double and the 28-year-old felt he would soon be reeled in by the later starters.
"There's some scores to be had out there and I think my lead will probably not last too long," he said. "I feel like someone will probably outdo me by a couple shots here today, at least.
"But obviously I'll hopefully be within reach after today and really looking forward to the next few days."
US Open and Masters Tournament winner Spieth was playing with World Number One Rory McIlroy and he outscored his partner with a 67.
The 22-year-old birdied the 11th but failed to get up and down from a greenside bunker on the 12th before picking up a shot on the 16th and chipping in on the 18th. He then holed from 12 feet for another birdie on the first.
Spieth made another birdie on the par three third after putting his tee shot to within five feet and a sixth birdie of the day at the sixth put the American right in the mix going into the weekend.
"It was definitely gettable today," he said. "I got off to a good start making birdie on my second hole, and then the one on 18 was a great spark to get things going, get a little confidence, a little pep in my step.
"I was staring one over on the round down and instead make the turn in two under. So that was a nice kind of two-shot swing in one shot.
"Then I was able to take advantage on the front."
McIlroy recorded a 71 to sit five shots off the lead and admitted he was "a little bit annoyed" at failing to take advantage of perfect conditions.
Playing his first tournament since the US Open in June after seven weeks out due to an ankle ligament injury, McIlroy made amends for a double bogey on the 18th by chipping in for eagle on the second and also carded two birdies and one bogey.
"I felt like tee to green I hit the ball pretty well, I'm probably just not as sharp with the short game as I would like to be," he said. "It was good to get the two shots back that I dropped on 18 and I gave myself good chances on the third and fifth, but did not take them.
"There's plenty of chances out there and if I can convert a few hopefully there is a low score in me.
"I felt like I played better than what the score reflected. A little bit annoyed. I felt like I should have got that ball up and down on seven and then I had a great chance on eight for birdie and didn't take that. A couple of days in a row where I haven't finished the round of golf the way I wanted to.
"I don't know if it's rust or I just didn't putt well, so maybe just work on that a little bit before I tee off tomorrow and it would be great to hole a few more putts, because I feel like I'm giving myself plenty of chances."
Stenson's six under round got him to two under for the tournament after an opening 76 and the Swede, who had eight birdies in his first 15 holes, would have gone even lower had he not had back to back bogeys at seven and eight.
"I didn't score well yesterday," he said. "I played all right, actually, I played a whole lot better than what the score showed and then it was just tougher conditions in the afternoon.
"It was, I guess, a good two-shot swing from playing in the morning to the afternoon. And that certainly didn't help when I was not scoring the way I should.
"So, yeah, at least good to see that I can get a good round in on this golf course, because I haven't managed that in the past and hopefully we've got another couple in us."
Marcel Siem fired a second consecutive 70 to sit at four under and Y E Yang, Brooks Koepka and Luke Donald were all alongside McIlroy and Stenson at two under.
Emiliano Grillo was one under for the tournament and heading for the weekend in his first Major despite a one over 73.
