The 24-year-old Ulsterman hit a third round 69 to move two clear of American Russell Henley with Scotland’s Russell Knox a further shot behind.
McIlroy has led from day one in Florida and maintained that form on Saturday despite three bogeys, offset by four birdies in a mixed third round performance.
He is now in the driving seat for victory in Sunday’s final round.
McIlroy said: “I’m happy to maintain the lead I had, to extend it by a shot and shoot under par.
“It was tricky conditions, the wind was stronger than it has been all week. I think anything under par, especially if you were in the last few groups, was a good score.
“If you can limit the damage as much as possible I think that’s the key, especially when conditions are like this.
“If I can just keep hitting the fairways and hitting the greens sooner or later they’re going to drop for me.
“I’m just looking for more of the same on Sunday. I’m two ahead. This course is all about putting your ball in play, trying not to make mistakes, picking up birdies when you can.