The two-time Masters champion showed signs of overcoming his slump and recent wrist injury with a 3-under par 68 in strong wind Saturday for a one-shot lead after three rounds of the Scottish Open.
Mickelson, playing on the weekend for the first time since winning the Players Championship on May 13, has a 54-hole total of 12-under 201. Gregory Havret of France, a co-leader after two rounds, trails by a shot after a third-round 70.
Steve Webster of England shot a 69 and is in third, three strokes behind Mickelson, who had withdrawn from the Memorial and missed the cut at the next two tournaments he played before coming to Loch Lomond for the British Open warmup. He hadn't had such a dismal streak since 1995.
Ernie Els finished with a 71 after four birdies and four bogeys to share sixth place with Lara and Mikko Ilonen.
Mickelson's round included a walk into the water at the third hole after his second shot hit the green and spun back into a pond. He wore waterproof pants to hit his submerged ball out to eight feet and holed the putt for a birdie.
Despite the wind, Mickelson managed to hit every fairway except one, the 13th.
"I should have played that more carefully for the stats because I've never hit all the fairways," he said.
After shooting 68 in consecutive rounds, he said his confidence is increasing as he prepares to take on Carnoustie next week.
"In 2004 I went in very confident in my game and finished third. But I think I need to put together one more good round here to have that same feeling," he said.
He has a chance to win just his second event outside the United States. His only victory overseas was the Tournoi Perrier near Paris in 1993.
"I have never played as well outside the U.S. as I would like, and especially in Scotland, the home of golf," he said. "It would mean a lot to have a championship from here. That would really be something special."