After wins in four of his first five events this year Els birdied the 15th and 16th and then drove the green at the downwind 359-yard 17th to take over at the lead.
But then the world No. 2 and defending champion, having two-putted for a third successive birdie, had a bogey on the 547-yard par-5 18th for the second straight day, leaving him with a 13-under-par 203 and tied with Forsyth and Lynn going into the final 18 holes.
"He showed he is human and does make mistakes," said Forsyth, who had built a three-stroke lead before settling for a 69 like the other two.
"There's always a fear that Ernie will go away, but it does not seem to be happening here," said the 29-year-old Lynn, who is seeking his first European tour victory. "All eyes will be on him tomorrow, so I will just see what I can do."
Els went in the lake for his closing six in the second round. He barely overcme the water this time as the ball came to rest on top of the wall lining the hazard. After contemplating playing the shot with the toe-end of his putter, he chipped it. But the ball ran to the back of the green and from there he three-putted for the third time Saturday.
Forsyth had a chance to jump back into sole possession of the lead on the 18th, but after laying up missed his nine-foot birdie putt.
A year ago Forsyth played with Els in the first two rounds of the event. Els shot 68-68 and went on to win, Forsyth had 77-72 and missed the cut.
Forsyth had birdie putts of nine and five feet at the seventh and eighth holes Saturday. They were his last birdies, but 10 successive pars kept him near the lead and give him a chance to win for the first time since the Malaysian Open title last year - a win that came after he had lost his European tour card the previous season.
There were no moves from Irish Ryder Cup trio Darren Clarke, Padraig Harrington and Paul McGinley. Harrington, who blamed poor early season concentration for not figuring more on the first two days, had a 71 and is 2-under,while McGinley four-putted from 15 feet on the 18th for his second double-bogey seven of the back nine, and is 2-over.
Both will be hoping for better in next week's Qatar Masters, but Forsyth withdrew his name from the event like 39 others with war against Iraq looking increasingly likely. Clarke, who also withdrew from the Qatar Masters, carded a 72 Saturday to remain 5-under.