Trying to become the oldest winner in tour history, the 64-year-old Haas birdied the par-5 16th and 18th holes to get to 11-under 133 on The Country Club of Virginia's James River Course.
"I've been out here too long to know that I can learn to expect anything," Haas said. "While I'm hopeful every day and I've been playing OK, the last couple weeks have not been very good, but this week has been much better. I love this golf course and it looks good to my eye. Most of the holes look like I'm going to hit a good shot, so I enjoy playing here."
Mike Fetchick set the age record of 63 years to the day in the 1985 Hilton Head event. Haas is second on the list, taking the 2016 Toshiba Classic at 62 years, 10 months, 7 days for his 18th senior title.
"That's a good way to say I'm old, 'experience,'" Haas said. "I think I'm very nervous most of the time when I play and today was no exception, but I continued to hit good shots and, hopefully, I can put one foot in front of the other, one shot at a time, do what I tell my son to do every time, you know? See if I can put some of those adages to work tomorrow."
Stephen Ames and Scott Dunlap were tied for second after the round that started in light rain. Ames had a 67, and Dunlap shot 68.
Defending champion Bernhard Langer had a 66 to join Billy Mayfair (67) and Woody Austin (68) at 9 under. Langer won the SAS Championship last week in North Carolina to take the season points lead. The 61-year-old German star has two victories this year and 38 overall on the 50-and-over tour.
The top 72 players qualified for the Charles Schwab Cup Playoffs opener. The top 54 on Sunday will get spots next week in the Invesco QQQ Championship in Thousand Oaks, California, and the top 36 after that will advance to the season-ending Charles Schwab Cup Championship in Phoenix.
Miguel Angel Jimenez, second in the standings, was tied for 23rd at 4 under after a 71.
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