The former World No. 1, who came into the day with a one-shot lead over Russell Henley, is seeking his seventh career win on the PGA Tour.
Brendon de Jonge moved into sole possession of second place at 10-under with a 6-under 64, while Henley (68) ended 36 holes alone in third at 8-under at PGA National Resort & Spa.
Lee Westwood (65) and Russell Knox (63) share fourth one shot further back.
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