The 35-year-old, who won the national title in 2019, posted a third round four-under 67 for a 15-under aggregate of 198 and moved clear of nearest rival, Sam Kiloh.
As the dominant force on the Arnold Clark Tartan Tour in recent years, O’Hara’s competitive instincts are undeniable but allied to that clinical edge is a tranquillity of mind that remains a vital weapon in the armoury.
“There are more things to worry about than golf so I don’t beat myself up too much on the course,” he said of this relatively carefree approach. “You’ll not do yourself any favours if you let the game get to you. If I have a bad hole I just forget about it and bounce back. That attitude really helps.”
O’Hara, who is also in the driving seat to retain his Order of Merit crown, had been locked at the top with Alastair Forsyth teeing-off in day three but it was Kiloh who became his main rival as the third round unravelled.
The Deeside pro, who is making just his second appearance in the national championship, leaked a shot on the first but roared back with a thrilling blitz of five birdies over his next six holes to vault into contention.
O’Hara, who reached the turn in three-under, was keeping it nice and steady and there was a significant swing towards the end of the round when Kiloh spilled a shot at 17 just as O’Hara was picking up a stroke behind him on the 16th.
“I’m playing smart golf and just trying to play it into the same spots each day,” added O’Hara of his considered approach. “On this course, it’s about giving yourself that second shot. You can get yourself into bother in the wee sneaky bunkers but I’ve managed to plot a nice way round.
“The leaderboard is still quite bunched and I know the others boys will come out firing on the last day. But I’ve got good experiences to fall back on when I’m in this position.”
Kiloh almost closed the gap on O’Hara when a birdie putt on the last reared up just half-a-roll short of the hole. His 67, though, left him with plenty to play for in a rare outing on the domestic circuit.
“I’ve only played four or five events this year due to family commitments and the fact I’m busy with my PGA training,” said the 27-year-old. “It’s a wee bit of a surprise to see my name near the top but, at the same time, I knew my game was in good shape.”
Forsyth’s bid for a first Scottish PGA title crown since 2000 suffered a blow with three bogeys around the turn but he rallied with a brace of birdies at 14 and 15 in a 70 to stay in the hunt at 12-under. Craig Lee, last year’s runner-up, slithered back to nine-under after a one-over 72.