Danny Willett made two quick birdies to take the lead early on day two of the World Golf Championships - Cadillac Championship.
The Englishman began the day two shots off the summit but made birdies on the first and second to move to six under, a shot clear of Phil Mickelson, Scott Piercy, Adam Scott and Jimmy Walker at Trump National Doral.
Piercy had held the overnight lead alongside Marcus Fraser but dropped a shot on the 11th, his second, while three dropped shots in four holes from Fraser saw him fall to three under.
Walker had two early birdies in his first eight holes, while Scott was one under for the day through five and Mickelson was level par.
World Number 15 Willett had spoken coming into this week of his desire to get to number one in the Official World Golf Ranking, and has made an excellent start to the season with his recent win at the Omega Dubai Desert Classic.
World Number One Jordan Speith made a birdie on the second to get into the group at four under alongside Paul Casey, Jason Dufner, Charley Hoffman and Bubba Watson.
Fraser has been in superb form of late with a win at the Maybank Championship Malaysia and a 15th-placed finish at the ISPS HANDA Perth International, but he found the water to double-bogey the third and dropped another shot on the next.
Jamie Donaldson was at three under having picked up a shot on his first hole, with Harris English and Billy Horschel also three off the lead.
Russell Knox, Anirban Lahiri and Bernd Wiesberger were a further shot back, with World Number Three Rory McIlroy in the group at one under.