Otto used a chip in birdie on the ninth and a long birdie putt on the 10th to take the lead from two to eight as his nearest challenger, Titch Moore, collapsed with a triple bogey and bogey.
Otto, who won the Nashua Masters in November, has a six-stroke advantage over Craig Lile heading into Sunday's final round. Lile posted a 3-under 69 on a day which saw him vault into second with birdies on five of his last six holes.
Just a stroke back of Lile is Trevor Immelman, whose improved a stroke each day, carding a 71,70 and then a 3-under 69 in the third round.
Immelman, winner of two events in the past three weeks and also a runner-up finish in that span, will have to make up seven strokes to catch Otto on Sunday. It's a position Otto is happy to be in.
'They must make 66 and I need a 72 for a play-off. Hopefully I will shoot better than a 72. If they come out and beat me, well, then well played by them. But they are doing the catching, not me, Otto said.
South African Desvonde Botes got onto the leaderboard Saturday by shooting a 7-under 65, though most of it came on the opening holes. His front-nine 29 included three birdies and an eagle two in his first four holes.