Tommy Fleetwood seized the lead at the Honda Classic with a third-round 67 but Shane Lowry's three-over 73 saw him slip down the leaderboard at Palm Beach.
Englishman Fleetwood added to opening rounds of 70 and 68 to sit on five-under-par overall, one shot bette than American Brendan Steele and two clear of his countrymen Lee Westwood and Like Donald.
Fleetwood's third-round effort was one of the cards of the day in testing conditions at the par-70 Florida layout.
"I could not ask for much more from today, it was a good day," Fleetwood said.
"Eventually I holed a couple of long ones today and it makes such a difference, and I holed some really crucial putts around that middle stretch."
Fleetwood added: "Tomorrow will be the same - to stand up and trust my driver, which is my strength, then to go out there and do something similar to what I did today."
Donald and Westwood both signed for 71s while two closing bogeys really hurt Lowry's chances of taking the title on Sunday.
The Offalyman dropped shots on the par-three 17th and, most frustratingly, on the par-five finishing hole. Although he managed to find three birdies elsewhere, an untidy opening nine - which included a double bogey at the fifth - had left him up against it.
Last year's British Open champion will start the final round six shots behind Fleetwood.
