Retief Goosen has endured mixed fortunes in his efforts to catch clubhouse leaders Robert Karlsson and Jeev Milkha Singh at the US PGA Championship.
The South African, attempting to surpass the two under par 68 shot by morning starters Karlsson and Singh, stormed to four under par after just seven holes, but gave back shots at the eighth and ninth.
A par followed at the tenth to leave him at two under, three ahead of Harrington, who has faded after a rapid start.
The Irishman, looking to add another Major to the back-to-back titles he has collected at The Open Championship, charged to three under with birdies at the first, second and third, but has since faltered.
He dropped strokes at the seventh and ninth before shipping another couple of bogeys at the 12th and 13th to go one over.
Ernie Els is a shot ahead at level par – he birdied the second and sixth but bogeyed the third and fifth – while Carl Pettersson of Sweden is in the clubhouse on one over.
Earlier, Sweden’s Karlsson could hardly have gotten off to a worse start with a double bogey six at the 435 yard first, but he bounced straight back with birdies at the second, third and fourth holes.
He collected further strokes at the sixth and eighth to go out in 32 before another birdie at the 11th took him to four under par. A pair of pars came at the next two as he continued to dominate the leaderboard, but back-to-back bogeys at the 14th and 15th took the gloss off a round of 68.
India’s Singh, meanwhile, looked set for a torrid day when he dropped a stroke at the first, but like Karlsson he recovered immediately.
He collected an eagle three at the second to go one under and then birdied the fifth to move into contention. Bogeys at the seventh and tenth took away his momentum, but Singh finished with a flourish by taking birdies at the 15th and 17th.
Sergio Garcia, who finished second at this event on his debut in 1999, is also in the hunt having carded a one under par 69. The Spaniard started on the tenth and was soon in his stride with a birdie at the 13th hole.
A bogey at the 498 yard 18th hole brought him back to level par, but he collected a stroke with a birdie three at the sixth. Garcia is currently tied with Phil Mickelson, who still has two holes to play.
England’s Paul Casey shot 72, while Colin Montgomerie finished six over.