Eaks finished with a 17-under 199 total to break the tournament record of 16-under 200 set by Haas in 2005.
'That's the hardest thing I've ever had to do,' said Eaks, who rallied from a five-stroke deficit to force a playoff with eventual winner Andy Bean last year at Rock Barn Golf and Spa. 'I always told myself that if I ever had that kind of a lead, it'd be the easiest thing to do to keep it, but it's not. ... I'll never do that again -- at least not intentionally.'
Eaks, who held a three-shot lead over Spittle entering Sunday's final round, extended his margin to six strokes with three birdies on the front nine at Rock Barn's Jones course. But Eaks bogeyed Nos. 11 and 15, and was forced to salvage par on Nos. 14, 16 and 17 after hitting into the rough.
'I just started playing too safe,' said Eaks, whose first Champions Tour win came in Endicott, N.Y., on July 15. 'As well as I was playing, I didn't think anybody could catch me. I probably did a couple things out there that I'd normally wouldn't do.'
That opened the door for Haas, who made six birdies Sunday for a final-round 66 to finish at 15-under 201. He had a chance for an eagle on the par-5 18th, but left a chip shot 3 feet short.
'I figured I needed something really, really special to catch R.W. ... but it just wasn't enough,' said Haas, whose 13th top-five finish this season pushed his lead in the Charles Schwab Cup standings to 386 over Brad Bryant, who tie for 15th. 'Still, it was nice to give him a little bit of a push.'
Eaks finished out his round by getting to the edge of the 18th green in two shots, then two-putted for birdie to close out the round.
'It's kind of hard to get out of that comfort zone and get back in it again,' Eaks said. 'Winning earlier this year, I still didn't believe I could win. Now that I've won twice, I can't wait to win a third time.'
Spittle, from Canada, birdied three of the last five holes to close with a 69 and tie Haas for second, his best Champions Tour finish in 13 career starts. His previous best was a tie for sixth in Birmingham, Ala., on May 20.
'It was great to have a chance to get in the last group ... and it was nice to birdie those last couple holes and sneak up on the board a couple spots,' said Spittle, who climbed from 61st to 48th in earnings this season.
Scott Simpson (69) was four strokes back at 13 under, and Des Smyth (67) and Gil Morgan (68) followed at 11 under. Nick Price (68), Keith Fergus (69) and Denis Watson (69) finished at 9 under. Jeff Sluman (70) tied for 15th at 7 under in his tour debut.