Couch's 269 broke the tournament record for this event. Richard Johnson set the previous mark of 270 in 1999.
Heath Slocum finished alone in third at 13-under while Danny Briggs, Mike Heinen and third-round leader John Patterson shared fourth at minus 12.
Couch started strong with a birdie at No. 1 and then seemed to find trouble on the third. His tee shot landed in the right rough and was under a tree. Couch hit a 30-yard cut-shot from 249 yards out and with a 3-iron, landed the ball 15 feet from the cup, where he two-putted for birdie.
'I pulled it off,' said Couch, referring to his amazing shot at three. 'That was the turning point. It just as easily could have been a bogey.'
Couch added birdies at nine and 11 before back-to-back birdies at 14. His wedge shot at 17 hit close to the pin but bounced 20 feet right.
'I couldn't believe it bounced right,' said Couch, talking about the approach at 17. 'I looked at my caddie and said 'that ball is meant to be there.' I knew I was going to make that putt.' He converted the birdie to go to 15-under and needed to save par at 18. Couch hit a low, draw shot from 170 yards at 18 that landed 20 feet from the cup. He two-putted from there to get into the clubhouse with the lead.
After Patterson failed to eagle the 18th, Couch had his first win on the Buy.com Tour.
'I feel like a weight had been lifted off my shoulders,' said Couch, who earned $76,500 for the win. 'This takes so much pressure off now. I wasn't sure I knew how to win again.'
Campbell was flawless on Sunday, scoring six birdies and no bogeys. He finished with a 65 for his 14-under total.
Slocum posted a 6-under 65 on Sunday and vaulted 12 spots to third.
Patterson struggled to a 70 in the final round and with a bogey at 18, tied for fourth. Briggs (67) and Heinen (69) joined Patterson in rounding out the top-five.
Defending champion Fran Quinn tied for 17th at 9-under 275.
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