Lian-Wei Zhang is alone in second place at 8-under-par 208, followed by Simon Yates and Prayad Marksaeng, who share third at minus-7.
Els owned a five-shot lead through 13 holes but stammered down the stretch. He scrambled to make pars at 14 and 15 but did not have the same fortune at the 17th and 18th.
Els badly pulled his tee shot at the par-3 17th and failed to save par. He left himself with a four-foot par opportunity at the last but the putt lipped out and Els left the course with only a two-shot lead after Zhang birdied No. 17.
'I started the day with a one-shot lead, now I have a two-shot lead,' said Els. 'It looked good for a while but some of the other guys played really well coming in so tomorrow is going to be a tough day.'
Els, who collected four birdies through his first 11 holes, is clearly the hottest player in golf. He blew away the field in a record-breaking performance two weeks ago at the Mercedes Championships and earned a hard- fought playoff victory over Aaron Baddeley last week at the Sony Open in Hawaii.
Despite being a heavy favorite Sunday, the No. 2 player in the world knows he will have to play well to hold off his closest competitors and win for a third time in as many weeks.
'There are some guys really close to me so I've just got to try and play the way I have been and hope for the best,' said Els. 'You have just got to try and hit fairways and greens and try and make putts and that is what I will try and do tomorrow.
'With a two-shot lead I really have got to knuckle down and play, it is a different ball game now. If you have five shots in hand you can maybe take it a bit easier but this is not really anything of a lead.'
Zhang, a 37-year-old from China, played steady with six pars to open his round but picked up two birdies around the turn to get closer to Els. Zhang notched a pair of birdies around a bogey at 16 to get within striking distance of Els.
Zhang is no stranger to big pressure situations. He owns victories over Nick Price and Colin Montgomerie in the old Alfred Dunhill Cup but Sunday's final-round pairing with Els will represent his toughest challenge in stroke play.
'I am very pleased with where I am in the tournament,' said Zhang, who shot a third-round, 3-under 69. 'I played well today but I will have to do even better tomorrow. I played with Ernie Els some years ago when he played an event on the Asian Tour, but he is a better player now and he will be very difficult to beat. But I will try my best.'
Yates struggled to a front-nine 38 but three birdies and a bogey in his last four holes gave him an even-par 72 for the round.
'Ernie is hitting his drives a bit erratically but he got away with it today,' said Yates. 'He is only three shots ahead of me so there is still a chance.'
Marksaeng rebounded from a pair of three-putts early in his round by draining birdie putts from 14 feet at the 13th and 20 feet at the 17th. He posted a 3-under 69 Saturday but realizes his chances of visiting the winner's circle with Els in front are slim.
'In the final round I will just try and do the same, hit fairways and greens and try and make some putts,' said Marksaeng. 'But the main thing I must do is hit the fairways as the rough is very difficult here. I cannot really see me catching Els, but second place would be great.'
Simon Khan, Maarten Lafeber, Chih-Bing Lam, Per Nyman and Mark Pilkington share fifth place at 5-under par.