Poulter had eight birdies over the final 13 holes to total 19-under 197.
Former winner Ricardo Gonzalez had his third consecutive round of 67 to finish one shot back. Gary Orr (70) and Christian Nilsson (68) are tied for third at 14 under
Darren Clarke, playing in his first event since the death of his wife from cancer last month, had a 69 to trail by 12 strokes. His five birdies were offset by bogeys at the 4th and 12th holes.
Clarke went into the 12th after three straight birdies, but a bad bounce left his drive under a tree that forced him to take a penalty drop on his way to a bogey-5.
'Today was not quite as good as the first two days, but I'll work that out,' Clarke said. 'I just got off to a tough start with two-putting everywhere.'
Poulter birdied the 6th to start a run of six birdies over eight holes as the hot weather dried out the course and brought scores down.
'I changed the putter this week, and I am just rolling the ball lovely,' Poulter said.
Second-round leader Padraig Harrington couldn't recover from a poor start that began with a double-bogey at the 2nd, 6th and 13th holes. He trails Poulter by seven strokes.
'I swung better and hit it better today, but around the greens I couldn't see the lines,' Harrington said.
Jose Maria Olazabal, who shot a 67 to move to 8 under, had a hole-in-one on the par-3 13th.