Liam Johnston set the clubhouse target midway through the second round of the 2020 ISPS HANDA Wales Open.
The 27-year-old from Scotland, who is yet to make a cut this season on the European Tour, compiled a second round 68 at The Celtic Manor Resort in more testing conditions.
At four under par he was one behind compatriot Connor Syme, who was continuing to show his aptitude around the 2010 Ryder Cup venue.
Syme had held the 54-hole lead in last week's Celtic Classic before finishing in a tie for third, and was level at the top of the leaderboard with England's Jordan Smith overnight.
At level par through 13 holes he remained five under, to lead by one from Johnston.
France's Romain Langasque was in the clubhouse at three under after a round of 68, with Smith, fellow Englishman Ashley Chesters, Spain's Nacho Elvira and Sweden's Sebastian Soderberg on the same mark out on the course.