Donaldson opened with three birdies in the first four holes of the second round and finished with a 6-under-par 66. He is at 11-under 133 for the tournament.
Ryan Moore, with the round of the day, had a bogey-free 7-under 65 and is tied with Henrik Stenson, who shot a second-round 67, for second at 8-under. Martin Kaymer (66) and Thomas Bjorn (70) are tied for fourth at 7-under.
Luke Donald, who was in the lead when play was stopped because of weather conditions in the middle of the first round Thursday, had a second-round 71 and is at 5-under for the tournament.
Sergio Garcia wound up with the first-round lead at 6-under 66 but was 1-over for the second round and is six strokes behind Donaldson.
Donaldson posted birdies at the first two holes and another at No. 4. He closed the front side with birdies at 8 and 9. He had his first bogey of the tournament at the par-5 10th when he had trouble getting out of a greenside bunker but pulled away from the field with birdies at the 13th and 14th holes.
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