Sean Crocker's sensational chip-in eagle at the 18th handed him a two-shot lead heading into the final round as he bids to secure his maiden DP World Tour title at the 2022 Hero Open.
The American showed impressive patience and a calm head on a testing third day at Fairmont St Andrews to remain on course for a wire-to-wire victory.
After making four birdies and a single bogey in his opening 12 holes on Saturday, Crocker ran into trouble at the 13th as he could not find a way out of the thick rough after two shots and also had a wall to worry about as he prepared to take his third.
He took time to think about his next step and, instead of taking any risks, he opted for a drop and walked away with a double bogey.
Crocker soon put that to the back of his mind, though, pulling off some battling par saves in breezy conditions before chipping in at the last to sign for a 69 and move to 18 under par.
Swede Jens Dantorp was alone in second two shots further back after posting a bogey-free 69, one ahead of home favourite David Law and Spain's Adrian Otaegui.
Crocker began the day with a one-shot lead but was caught at the summit in the early stages of his third round after opening with four straight pars.
He broke that run with a birdie from 22 feet on the short fifth before following up with another gain from close range at the par-five sixth.
The American made it a hat-trick of birdies when he converted an eight-foot putt at the seventh but a bogey on the eighth brought him back down to earth.
Crocker did well to save par at the ninth after clearing the green in two, heading to the turn with the one-shot lead he started the day with.
A good up-and-down at the tricky tenth meant he walked away from there with a par before he missed his lengthy birdie attempt on the par-three 11th and had to settle for another par.
After recovering from an errant tee-shot at the 12th, Crocker sent his third to three feet before rolling in the birdie putt to return to 18 under.
But he found trouble at the 13th, with his ball in the thick rough after both his first and second shots.
After thinking long and hard about what to do next, he opted to take a drop and went on to make a double bogey, but at 16 under he remained one clear of the chasing pack.
Crocker made a great two-putt par from 63 feet on the 14th before saving par again at the next.
He was unable to knock in his tricky birdie effort at the 16th but holed the return putt to stay one ahead.
Crocker was unfortunate not to birdie the difficult 17th after his long-range putt lipped out but he made amends at the last.
After flying the green with his second shot, Crocker chipped in to give himself a two-shot cushion at the top of the leaderboard.
Speaking about his remarkable finish, Crocker said: "That was a nice little bonus on the 18th. I was trying to get it up and down for a birdie but to see that ball drop was pretty cool."
Crocker was pleased with the way he responded after choosing to take a drop at the 13th, adding: "I was in control and it was either chip out or we take a chance and that could be the tournament over.
"I think we made the right decision by taking the drop and trying to keep the score down as much as we could.
"Even before I called over the rules official I wanted to have a go at it but every time I got near the ball I could see bad things happening.
"The best thing that I did in this round was during that whole situation I got a little frustrated as I was figuring out what to do. The moment we took the drop and I hit it away I just forgot about it.
"From there I was like, 'I’m still around the lead, let’s just make some pars and if something drops, it’s fine'."
Crocker admitted it would be special to get his hands on the trophy.
"It’s nice to have a bit of room but I also know those gaps can be closed very quickly," he said. "Just got to play my own game tomorrow and see what we can do.
"It would probably be the most special day of my life (to win this week). I play golf for the love of it, for trophies and all that stuff. It’s been a long time since I’ve held something shiny so it would be a nice little present."
Meanwhile, Englishman Graeme Storm had a day to remember after securing a hole-in-one at the difficult 17th hole, claiming the £20,000 prize.