The 29 year old carded a seven under par 64 on the testing East Course at Royal Johannesburg & Kensington Golf Club.
Elson narrowly lost his European Tour card at the end of 2010, but by reaching the halfway stage bogey free he has given himself every opportunity of earning a new one.
Having opened with a 65 on what is widely acknowledged as the easier West Course, Elson burst into life with five straight birdies from the fifth in his second round.
He picked up another shot at the 11th before play was suspended for two hours due to the threat of lightning.
On the resumption, he splashed out of a greenside bunker to two feet on the par five last to reach 13 under par.
Alongside him were South Africans Garth Mulroy and Martin Maritz.
Mulroy also carded a 64 on the East lay-out, including an eagle, seven birdies and two bogeys.
Overnight joint-leader Maritz had opened with a sensational 62 on the East Course, but was also finding the going good on the West Course as he reached the turn three under before joining the leaders with another gain at the 11th, hitting his approach within two feet.
Another South African - James Kingston - then made it a four-way tie at the top when he reached ten under for the day with two to play, his tenth birdie coming courtesy of a 12 footer at the par three 16th.
Defending champion Charl Schwartzel was level with his compatriot Thomas Aiken in a tie for fifth at 12 under.