Sluman, whose only major crown on the regular tour came at the 1987 PGA Championship, edged Fred Couples by one stroke and was two in front of Duffy Waldorf and Peter Senior.
"I kept the ball in the fairway all day," Sluman said. "The wind was absent out there."
If Lehman wins, he will join Hale Irwin as the only players to capture a Champions Tour major tournament three times in a row.
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