Rod Pampling is three behind after a rollercoaster round of 70 kept the 47-year- old in contention for his maiden national championship, while Scott is a further shot back at 7-under after salvaging a 71 with two late birdies.
But Ogilvy is the man they all must catch after making the most of the favourable early morning conditions to card a front-nine 30 courtesy of birdies at the first, second, sixth, seventh, eighth and ninth holes.
The 2010 Open champion iced his round with a stunning approach on the 18th for a tap-in birdie three.
"To be honest, I didn't really see 64 on the first tee," Ogilvy said. "But after going out so well on the front nine I kind of started seeing a score like that. It's always a nice feeling. I'm back in the mix."
And now that he is, Ogilvy admits he'd cherish winning his national championship - once regarded as golf's fifth major back when Nicklaus, Arnold Palmer, Player - victorious a record seven times - reigned in the 1950s, 60s and 70s before Greg Norman saluted on five occasions in the 80s and 90s.
"It would be great. Obviously, the list of winners on this trophy is about as good as any trophy in the world," Ogilvy said.
"And the list of multiple winners on this trophy probably is as good as any other trophy in the world - Gary, Jack, Greg. It would be pretty nice.
"As we all end our career and we look back, this one is going to be right up there with one of the most important tournaments we've played and satisfying one to win."
Ominously, after claiming to have felt "brainless" on the greens during the first two rounds, Spieth warned he was coming to grips with the poa annua grass in the nick of time and rolled in six birdies yesterday.
Despite predicting a winning score of about 12-under on Thursday, Spieth suspects he'll probably need to shoot in the mid-60s to reel in Ogilvy and keep the rest of the chasing pack at bay.
"I like the position we're in," he said.
So will Fox as he continues to fly under the radar.
- AAP