Bernd Wiesberger doubled his overnight advantage as the final round of the Portugal Masters began at Oceânico Victoria.
The Austrian, twice a European Tour winner already this season, remained 13 under par after four straight pars.
However, his closest challenger and playing partner Ross Fisher three-putted the fourth for bogey to drop two behind.
He was level with New Zealand’s Michael Campbell on 11 under par.
The 2005 US Open Champion, who has suffered a serious slump in form since that win at Pinehurst, birdied the first and fifth to move into contention for a first win in seven years.
In the testing wind, Wiesberger and Fisher both birdied the long fifth but the Vienna golfer failed to get up and down from sand at the difficult seventh.
They were 13 under and 12 under respectively - as they were at the start - while Campbell made up for a bogey on the seventh with his third birdie of the day on the next and was still in touch two behind.
