Drysdale, who is bidding to land a breakthrough success in his 519th start on the circuit, had his nose in front with four holes to play in the third round at Karen Country Club in Nairobi.
But back-to-back bogeys at the 15th and 16th, coupled with birdies from Harding at those two holes, delivered a sting in the tale for the 46-year-old Scot.
Both players birdied the last after brilliant approach shots, but it’s advantage Harding, who is bidding to make it back-to-back wins on the same course after already landing the Magical Kenya Open last Sunday.
Helped by that strong finish, the 35-year-old carded a five-under 66 to sit on 17-under, three shots ahead of Drysdale, who signed for a 69, and five others.
On the back of a 65, Calum Hill is in a group a shot further back, with Liam Johnston (66) also still in with a shout, even though Harding, who was 21-under in winning the first leg of this double-header, looks a difficult man to catch in this vein of form.
“Justin’s obviously doing great and I told him just there to give us all a chance tomorrow,” said a smiling Drysdale, who has finishsed second four times in his career. “He’s playing very steadily and obviously loves this place.
“But we’ve to take advantage of holes six to 12. There are three or four eagle chances in that part of the course, so a low one is required.”
Drysdale birdied the fourth, seventh and 11th as he moved into the lead. His two dropped shots thereafter were untimely but, helped by that birdie to finish, he’s still right in the mix alongside South African pair Darren Fichardt and Daniel Van Tonder, Thailand’s Jazz Janewattanond, England’s Marcus Armitage and Norwegian Kristoffer Reitan.
"I feel like I’ve hit the ball well and played well but, if two under is my bad day, I’ll take it,” added Drysdale.
Hill, who tied for eighth last week, is in the mix again after producing a nine-birdie salvo, including one to start and finish as well as three in four holes around the turn as his new partnership with experienced caddie Phil Morbey continues to prosper.
“I gave myself a lot of chances and made a lot of birdies, having putted well, so it was a good day,” said the three-time Challenge Tour winner.
“It’s not necessarily going to be a putting competition tomorrow, not round this course as if you hit it a little bit astray you can make some bogeys pretty quickly.
“Hopefully I can turn up tomorrow and have another good day. I’ll probably need to match today or a little better to have a chance. We’ll see what happens.”
Helped by an eagle and six birdies, Johnston was on course to sit alongside Hill heading into the last day before dropping a shot at the last.
Richie Ramsay, who signed for six birdies in his 68, sits on eight-under, two ahead of Daniel Young, who was four-under for the day through 12 holes before dropping two shots over the closing stretch for a 69.