He made a 50-foot birdie putt on the 17th hole that allowed him to join a six-way tie for second.
John Senden closed with a 67 and was a runner-up for the second straight year, both times finishing about an hour before the leaders. He tied for second with Cink (74), Ryuji Imada (68), George McNeill (69), Troy Matteson (69) and Billy Mayfair (72).
The Copperhead Course played nearly two shots over par, making it the toughest track on tour this year. O'Hair's winning score of 280 was the highest ever at Innisbrook. But he was the only player to shoot par or better all four rounds, and he saved his best for Sunday.
He got into the mix with a birdie on the opening hole. His chip from behind the 11th green to tap-in range for birdie pulled him within one shot. Then came a couple of par putts in the 4- to 5-foot range, to stay in the lead.
After a 7-iron to 30 feet below the hole on the 15th, O'Hair raised his arm when it dropped in the center of the cup.
"One of the best putts I've ever hit in my life,'' he said. "With 10 feet to go, I knew it was in the hole. From there, I was just trying not to throw up on myself.''
But he couldn't stop the tears when it was over, especially remembering the pep talk last week from his father-in-law, Steve Lucas.
"He told me how he believed in me, how he felt I was on the right track, and if I started believing in myself, everything would happen,'' O'Hair said. "I didn't believe him. But I guess he was right.''