Graeme McDowell shot a sparkling 64 to give himself the chance of a second Barclays Scottish Open title in four years - but last year's US Open Champion had company at the top at Castle Stuart Golf Links in the form of Scott Jamieson.
The 27 year old Challenge Tour graduate from Scotland was actually four shots clear at one point, but he double-bogeyed his penultimate hole and had to settle for a 66 and matching 11 under par halfway total.
McDowell was down in joint 30th spot after his opening 69 at the stunning new venue, but an eagle at the long 12th and four birdies enabled him to turn in 33 and further birdies came at the two par fives on the outward half.
Jamieson, with four top six finishes already in his rookie year, eagled the 18th and second - and that after five successive birdies from the 11th.
But he came up short of the green on the 218 yard eighth, left his chip on the fringe and three-putted.
"That was disappointing, but it's exciting to be in this position in Scotland and to get my first win here would be fantastic," he said.
Compatriot Peter Whiteford and Spain's Jose Manuel Lara were one behind with three to play, with Argentina's Angel Cabrera and Belgian Nicolas Colsaerts nine under after rounds of 64 and 66 respectively.
Justin Rose (67) was eight under, Padraig Harrington and Ernie Els one further back and Phil Mickelson - in danger of missing the cut after his first day 73 - up to four under after an eagle on the second and then two birdies.
Overnight leaders Lee Westwood and Mark Tullo, both of whom started with seven under 65s, were among the afternoon starters.
McDowell said: "It was a good day's work obviously. Conditions were easy and the course was there for the taking a little bit.
"But it was nice to get the low juices flowing. It's going to give you some confidence and the art of going low is a very important art.
"The course does not pose much of a challenge off the tee, but it's tricky around the greens and it gives you a test."
Mickelson parred his last three holes for a 67 and four under aggregate, which should see him safely through to the weekend unless there was even more spectacular scoring later in the day.
Whiteford joined McDowell and Jamieson on 11 under with a closing birdie for a 66, while Lara matched the round and was one behind.
Westwood was just starting as the first day of the rain arrived and he ran up a bogey six at the second to fall five behind.
It took Westwood until the long sixth to get back to seven under and by then he had been joined by Colin Montgomerie, whose pursuit of an Open Championship place continued with birdies at the second and third.
At 3pm, however, play was suspended because of the threat of lightning in the area.
