Langer, champion in 2010, leads Tom Pernice Jr, who shot a four-under 66, Tradition winner Tom Lehman, Senior PGA Championship winner Roger Chapman, John Huston and Corey Pavin, the latter four of whom all recorded a round of two-under 68.
The German opened with three straight birdies before adding back-to-back birdies at the sixth and seventh to make the turn already three-strokes ahead.
The 54-year-old again recorded three successive birdies on the 10th, 11th and 12th as he headed for the clubhouse.
But a double-bogey at the 13th saw Langer run into a spot of bother and, despite another birdie at the 15th, the German ended with a bogey on 18 that saw his once five-shot lead pulled back to three (later extended to four again as other rounds went his way).
"Hoping to go really low and then made an error on number 13,” said Langer.
“Really wasn't that bad a shot with the four-iron. Just hit it a little high on the club and came up two yards short in the rough and hit a bad chip shot and a bad short putt and made double-bogey.
"The only difference really was just I made some putts. I probably played worse than I played the first two days.
"The first two days I made very little, and I guess the course owed me some. I made a bunch of putts today."
Fred Couples, runner-up in 2010 when Langer won the title, holds a share of seventh (alongside Fred Funk, Jay Haas and Dick Mast) after a five-under round of 54.