SEA ISLAND, 25 Oct, 2014 (AFP) - MacKenzie was joined at 12-under-par 198 by fellow American Andrew Svoboda, who carded a four-under 66 on the Seaside Course at Sea Island golf resort.
MacKenzie is aiming for his third USPGA Tour title, while Svoboda is searching for his first win on the US tour.
Second-round leader Russell Henley managed a two-under 68 in the third round and dropped into third place at 11-under.
Stewart Cink fired a seven-under 63, the low round of the day, and soared into a share of fourth place at nine-under-par 201.
He was joined there by defending champion Chris Kirk (66), Brendon de Jonge (69), Fabian Gomez (68) and Andrew Putnam (66).
Leading scores after Saturday's third round of the USPGA Tour's The McGladrey Classic (USA unless noted, par-70):
198 - Will MacKenzie 65-68-65, Andrew Svoboda 66-66-66
199 - Russell Henley 68-63-68
201 - Stewart Cink 69-69-63, Brendon de Jonge (ZIM) 68-64-69, Fabian Gomez (ARG) 67-66-68, Chris Kirk 68-67-66, Andrew D. Putnam 68-67-66
202 - Mark Wilson 67-66-69, Ken Duke 67-69-66, Scott Piercy 67-67-68
203 - Rory Sabbatini (RSA) 67-70-66, Kevin Kisner 69-68-66, William McGirt 68-67-68, Michael Thompson 65-71-67, Ben Martin 70-68-65, Cameron Tringale 68-68-67, Hudson Swafford 70-67-66, Robert Streb 69-66-68