Darren Clarke of Northern Ireland fired a spectacular round of 64 to move into a share of second with Phillip Price at 10-under-par 203.
Els has put together three solid rounds in his final preparation before defending his British Open title next week at Royal St. George's. However, Els doesn't have next week's major in mind but rather a victory this week, which would be his third of the 2003 season on the European Tour.
'I want to go out tomorrow and play the way I have been playing,' said Els, who also has two PGA Tour wins to his name in 2003. 'There is a lot of thinking going on and I will have to be patient and stick to my guns.'
Els stood four strokes clear of Price to start the day and picked up his first birdie of the round at the par-5 third. He then parred his next five holes before knocking his approach inside three feet for a birdie at the par-4 ninth.
The South African birdied the 14th and hit his second shot to 12 feet at the 15th to make it two in a row. He found trouble with a bogey at the 16th, his second dropped shot of the tournament, but managed to recover at the par-4 last.
Els hit a brilliant approach at the 18th that landed five feet from the cup. As steady as always, he drained the short birdie putt for a comfortable margin with one round to play.
'I saw a few of the flags for tomorrow and they look quite tough so it's going to be difficult to shoot very low which will maybe make it a little bit easier for me,' said Els. 'But I've still got to go out and play my game the way I've been playing and make some more putts.'
Clarke, who is seeking his first title of the year, rocketed up the leaderboard with four birdies over his first nine holes.
'Darren is very capable of shooting low scores,' Els said of Clarke, whom he will play alongside on Sunday. 'It'll be fun. I played with him the first two days and he looked like he was striking the ball well.'
The Ulsterman added back-to-back birdies starting at the par-4 14th and capped off his round with a birdie at the last.
'It was good to shoot a low number again and I am hitting a lot of very solid putts so I have a chance,' said Clarke, whose last victory came at the 2002 English Open. 'It's possible.'
Price has found himself in contention for the second week in a row. After winning the European Open last week at The K Club, Price tallied two birdies on the front nine but stumbled with a bogey at the 11th.
The Welshman countered with a birdie at the par-5 13th and rolled in a lengthy birdie putt at the 16th en route to a 68.
'Five shots is a lot behind, the way Ernie is playing, but you never know,' said Price. 'If I get off to a good start and maybe harass him a little, it might not be so easy for him.'
After a par at the first, Peter O'Malley collected four consecutive birdies and was well on his way to a remarkable round of 62 to move into fourth place alone at 8-under-par 205. O'Malley had previously shot 62 at this event in 1992, when he captured the title at Gleneagles.
Peter Lonard and Ian Poulter finished one shot further back at 7-under-par 206.
Tim Clark, Bradley Dredge, Alastair Forsyth, Gary Murphy, Terry Price, Iain Pyman and Shaun P. Webster followed at 6-under-par 207.
Phil Mickelson carded a 1-under 70 to finish in a tie for 49th at 1-over- par 214. Fellow Americans John Rollins and John Daly struggled with rounds of 76 and 77, respectively.