It's the first time Mickelson has had the 54-hole lead on the PGA Tour since the 2013 U.S. Open, and he hasn't won since the 2013 British Open at Muirfield. He will be going for a record-tying fifth victory in the Pebble Beach Pro-Am.
Hiroshi Iwata of Japan was two strokes back after a 69 at Spyglass Hill.
Mickelson was at 16-under 199.
Jordan Spieth had to get up-and-down for par on the 18th hole at Pebble Beach for a 74 to make the cut on the number.
