The South African did not drop a shot all day to finish 14 under par and in pole position to win the title for a fifth time.
Fellow home favourite and former champion Retief Goosen is Els' closest challenger on 12 under after adding a 68 to his opening 64.
Frenchman Romain Wattel is a further shot back on 11 under after a 66, with Open Champion Louis Oosthuizen (67) and Charl Schwartzel (69) another shot back.
With 36 holes scheduled for the final day after most of Thursday's play was abandoned due to persistent rain, the chasing pack still have plenty of time to overhaul World Number 12 Els.
The field was cut to 50 instead of 65 ahead of 36 holes on Sunday, but Els is not concerned about the extra round.
"We use to do it when we were younger and when we were playing amateur golf," he said. "It wasn't a problem then so I don't think it will be a problem tomorrow.
"In fact, I like it because you stay in the game and you keep going. Sometimes when you play a round, you are going to sleep on it and now tomorrow you can just continue playing. I like that."
Speaking about his round, Els added: "It's never easy, but as I said yesterday, I felt really good.
"Again I feel like I'm hitting the ball quite nicely and that gives you some confidence on the tees.
"I don't want to look too far ahead. I'm quite patient this week, I'm playing within myself and I'd like to do that again tomorrow."
Teenager Wattel, who is playing his first European Tour event since turning professional after graduating through Qualifying School, was pleased with the way his first two rounds have gone.
"For the moment it's a nice position to be in," he said. "It's perfect and I couldn't have expected anything more than this. I played quite solid golf.
"It's really nice to see my name up there with such players. They've won Majors and are amongst the top players in the world, so to be up there with them is great."
With rain again forecast for tomorrow, Oosthuizen was hoping to at least play a further 18 holes to try to overhaul Els.
"I've been keeping track and hear there's rain," he said. "But hopefully it stays away and we can get at least another 18 in.
"I think everyone will be disappointed if we can't get 36 in."
Defending champion Richie Ramsay of Scotland missed the cut after following up yesterday's 71 with a 74, while Spaniard Pablo Martin - who won last week's Alfred Dunhill Championship - also missed out after successive 71s left him two under and one outside the cut.