He posted a 16-under 196 total, while fellow American Kevin Chappell, the halfway leader, shot 68 for 13-under, with Northern Irishman McDowell (65) four shots off the pace.
After already posting four runner-up finishes this year, the latest two weeks ago at the WGC-HSBC Champions in China, Kisner said he was not particularly nervous as he seeks to his breakthrough.
“I haven’t been in this position with a three-shot lead going into the last day all year. It’s going to be a type of new atmosphere but I’m just going to keep playing the way I’m playing.”
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
The 31-year-old, who recently bought a second home on Sea Island, has worked his way up to 25th in the world rankings without posting a victory.
“If I keep hitting the ball the way I am, I just need to hole some putts,” he said.
McDowell, meanwhile, suffered a setback in his quest for a second successive win when he picked up his ball in the fairway on the first hole.
The PGA Tour had played lift, clean and place for the previous 10 rounds (over three events) due to wet conditions, but did not invoke the rule on Saturday.
“I got my tee out and picked the ball up to clean it,” said McDowell.
“I got my yardage and I go through my normal routine and without even thinking. My playing partner, Michael Kim, was looking at me funny and I’m like, ‘what’s he looking at?’ and then he says to me ‘what are you doing?’
"And I’m like ‘oh my goodness, you absolute idiot’. The first time I ever did it. Hopefully my last time.”
McDowell, who won the OHL Classic in Mayakoba on Monday, shrugged off the mistake, took his one-shot penalty, and put the incident quickly behind him to salvage par by hitting a nice seven-iron to 10 feet and holing the putt.
“It was a bit of a potential day-changer ... instead of bogey there and who knows what could have happened today.
“I was very conscious of making sure I made four … it makes for a better story if it’s got a happy ending.”
(Reporting by Andrew Both in Cary, North Carolina; Editing by Larry Fine)
