The seven-stroke margin Jacquelin owns is the largest on the European Tour this season through three rounds. He is in position for his first win on tour after having posted four second-place finishes over his 10-year career.
Jacquelin's name could be all over the record books this week if it were not for the lift, clean and place rules in play due to wet conditions.
He tied the 36-hole tournament record of 128 and his three-round total of 192 would have bested Retief Goosen's 54-hole mark of 196. Jacquelin's 192 total also would have tied the European Tour record set by Tiger Woods at the NEC World Championship five years ago.
Jose-Filipe Lima carded a 4-under 67 to move into a share of second place at 14-under-par 199. He was joined there by Dar who shot 68 in round three.
Paul Lawrie, the 1999 British Open champion, is one stroke further back after a round of 66. Stuart Little also shot 66 to take fifth place at 13-under-par 200.
Jacquelin got off to a flying sart in his third round. He birdied the second and third to quickly move to 16 under. The Frenchman then two-putted for birdie on the par-5 fourth at Club de Campo.
The 33-year-old birdied the par-5 seventh to stretch his lead to six strokes. Jacquelin missed the green at the par-3 ninth and was unable to save par on No. 9 for the second round in a row.
Jacquelin quickly erased that error. He ran in an 18-foot birdie putt on the 10th and a 14-footer for birdie at 11 to get to 19 under. Jacquelin parred four straight holes before extending his lead.
He dropped his second shot within 6 feet of the cup to set up a birdie on the 16th. Jacquelin drained a 25-footer for birdie at the last to take the huge third-round lead.
'I've been on top of leaderboards before a few times, but never by seven shots,' said Jacquelin. 'I've got a few to play with and I intend to just relax and enjoy the finish. I could have been a few more under par if I hadn't missed the short putts, but the key to me doing so well is because I'm rolling the ball so well on the greens and I only missed one fairway today.'
Lima traded a birdie for a bogey from the fourth. He then converted back-to-back birdies from the seventh to get to 12 under. After five pars in a row, Lima birdied the par-5 14th before closing with a birdie on the 17th.
Clarke was steady throughout this round. He started by parring the first six holes, then the Ulsterman birdied seven and eight to get to 13 under. Clarke was within four shots when Jacquelin bogeyed the ninth, but Clarke could only muster one more birdie on the 10th. He closed with eight consecutive pars.
'He played fantastically. A 64 was the worst score he could have possibly shot,' said Clarke of his playing partner, Jacquelin. 'I've lost a six-shot lead, at the 1999 European Open, but he's going to be hard to catch. He's playing unbelievably well.'
Robert-Jan Derksen, Anders Hansen and Miguel Angel Jimenez each carded rounds of 5-under 66. They share sixth place with European Ryder Cup captain Ian Woosnam (68) at 11-under-par 202.
Colin Montgomerie, who leads the European Tour Order of Merit, paces a group of eight players one stroke further back at minus-10.