The exciting American, winner in Singapore last week, kept up his spectacular scoring at the Steyn City course on Saturday, shooting a seven-under-par 64 to move to 21 under for the LIV Golf South Africa event and hold a two-shot lead over home favourite Branden Grace.
Cameron Smith, who reckons he's feeling better than he has done for some time, led the Australian challenge with his second 66 of the week, but lying in joint-12th place at 14 under, will need a spectacular finish to really get into the picture on Sunday.
As well as Grace's individual bid, the vast galleries will be cheering for the all-South African Southern Guards, who lead the team event by two with Grace (64), Dean Burmester (65), Louis Oosthuizen (64) and Charl Schwartzel (65) having moved to a remarkable combined total of 60 under for the week.
DeChambeau chipped in at the par-four fifth hole and also eagled the par-five 10th with a 15-footer, adding three more birdies in a flawless round at the Jack Nicklaus-designed course.
"Tomorrow is going to be a great day," said the 32-year-old leader De Chambeau, who's feeding off the cheers of the noisy supporters who were dubbed by Oosthuizen, with a smile, as the "rowdy boys."
"Gracey is playing some incredible golf. He's got a huge hometown support, and it's cool to feed off of that energy, so hopefully there's a little bit more energy, and I can kind of feed off of that. I like it."
Grace is one ahead of Mexican Abraham Ancer (64) and Spain's Jon Rahm (64), who are on 18 under.
Queeslander Smith had another impressive day with a round that featured five birdies and no bogeys, while his Ripper GC team were seventh in the team event on 40 under, with Elvis Smylie tied for 24th on 11 under after his 66.
Marc Leishman is on eight under in 40th spot following a 66, with Lucas Herbert one place and one shot further back after his 68.
Phil Mickelson, playing in his first LIV event of the season due to a family health matter, carded a 64, improving on his first two rounds of 75 and a 67.
"I really missed it. I'm glad I'm here," said the 55-year-old. "I wish I played better the first day, but I'm really having fun. It's just fun to be back playing."
