Jorge Campillo joined Erik van Rooyen at the top of the leaderboard as the fourth Rolex Series event of the season was set for a dramatic conclusion at the Dubai Duty Free Irish Open hosted by the Rory Foundation.
The South African entered day four at Ballyliffin Golf Club four ahead but three bogeys in four holes from the sixth saw him turn in 37 and slip to 12 under.
Spaniard Campillo was six under through 13 holes to join him at the top, one shot clear of New Zealander Ryan Fox and Scot Russell Knox.
South African Zander Lombard was then at ten under.
Campillo got off to a flying start, holing an 18-footer on the first, adding another birdie on the next and then putting his second to eight feet on the fourth to set up an eagle.
That saw him join Joakim Lagergren in second but Fox was heading in the other direction after dropping a shot at the first.
The inviting pin at the fourth was giving the players plenty of opportunity and Knox was the next to take advantage, putting his second to six feet for an eagle and a share of second.
Fox holed a 30-footer on the same hole for an eagle of his own to get within three and he was soon joined by Campillo who holed from similar distance on the eighth.
When Campillo birdied the ninth to turn in 29, the lead was briefly down to two but Van Rooyen was back three ahead as he got up and down to birdie the fourth.
Lagergren also made a gain on the par five but he double-bogeyed the next after finding two bunkers.
Knox birdied the sixth to join Fox at 11 under and a first bogey of the day from Campillo on the 11th saw him fall into that group.
That meant the lead was briefly back up to four but Van Rooyen made a first mistake of the day with a three-putt on the sixth.
It was back-to-back bogeys when he found sand off the seventh tee and with Knox holing a 12-footer on the tenth, the lead was down to one.
Knox gave that shot straight back on the next and he was replaced one off the lead by Campillo, who birdied the par five 13th.
Van Rooyen had stopped the rot with a par on the eighth but he went a long way right off the ninth tee and the resulting bogey meant there was a tie at the top.
Lombard made three birdies in four holes from the tenth after picking up a shot on the fourth to surge up the leaderboard.
Danny Willett was level par after ten holes alongside Lagergren at nine under, two clear of defending champion Jon Rahm, Raphaël Jacquelin, Matthieu Pavon, Thorbjørn Olesen and Peter Uihlein.
