On a day when many of the front-runners turned in high scores -- Friday's co-leader Kim Felton shot 79 -- Nitties and Allenby had 54-hole totals of 10-under 206, a stroke ahead of Stuart Appleby (68).
'I really did hit some unbelievable shots out there because it was very tricky,' Allenby said. 'Today was one of those days where I could've shot quite a few lower than what I am. But it's the Australian Open. It's a tough tournament to win and I've got a lot of respect for it and for the field.'
Craig Parry, who followed his course-record-tying 64 with a 70 Saturday, is tied for fourth with Nick O'Hern, who shot 72 Saturday after sharing the second-round lead with Felton.
American Brandt Snedeker was sixth after a 70, three strokes back, followed by former two-time champion Aaron Baddeley after a 69.
Felton was 1 under for the tournament and tied for 37th after Saturday's 7-over round. Australian Andrew Bonhomme, who was one stroke behind going into Saturday's round, had an 81 and is 2 over and tied for 54th.
American Lee Williamson, also just a stroke off the lead after Friday, shot 76 and fell seven strokes behind.
O'Hern started off eagle-birdie, but double-bogeyed the par-5 fifth. Felton had a bogey on the first, a quadruple-bogey seven on the par-3 fourth and chipped in from off the green on the par-5 18th for a seven, saving him from an 80.
Appleby, who missed the cut at last week's Australian PGA, hopes he'll be in the hunt Sunday for his second Australian Open title.
'I'm not sure what I have to do,' Appleby said. 'I know I have to do something like today, think like today, commit like today and play like today and that still might not be enough. It's going to be a good old test for everybody.'
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