Winner of the WGC-Accenture Match Play in Tucson and up from ninth to third in the Official World Golf Ranking as a result, the 33 year old covered the first 11 holes of his third round at the WGC-Cadillac Championship in Miami in a superb six under par.
From 11th place and four strokes adrift of American Hunter Mahan at halfway Donald burst into a share of second spot and only one behind Mahan.
While Mahan went to the turn in 33 with birdies at the first, third and sixth, playing partner Martin Kaymer - his conqueror during the Match Play - drove into the water for a double bogey at the third and dropped another shot two holes later as the World Number One slipped back.
Donald's 60 yard pitch to three feet on the long first was an instant boost and he picked up further strokes at the fifth, sixth and eighth before starting for home with two more birdies.
On 11 under par he was joined by another American Nick Watney, while two behind were Scot Martin Laird, Italian Francesco Molinari - he won the last of the World Golf Championship series last season in Shanghai - Australian Adam Scott and Mahan's Ryder Cup team-mate Dustin Johnson.
Ireland's Padraig Harrington was only three back, but Northern Irishman Rory McIlroy had five strokes to make up after mixing three birdies with three bogeys in his first 11.
Donald, possibly the sport's best bunker player, showed it again on the 14th.
He drove into sand and was close to the lip, but from just over 150 yards hit it to seven feet and made it for his seventh birdie and a tie of the lead.
With Watney making four on the long 12th and Mahan having six pars in a row, the three of them were 12 under, one ahead of Johnson.
Donald made his only mistake of the day on the last, driving into the right-hand rough and missing a nine foot par putt.
He would have certainly taken his 66 before the start, but he was two behind Watney and Johnson on 11 under.