He owes much of that lead to Carl Pettersson, who lost the lead and lost control with a five-putt from 40 feet on the 16th hole that sent him to a 76, five shots behind.
'Just a mental block,' Pettersson said. 'I'll try to forgot about it and play well tomorrow.'
Hamilton was at 14-under 202 and will play in the final group with Fredrik Jacobson of Sweden, who had a 70.
Chris Riley, who has not made a bogey in his last 43 holes on the Sunrise course, holed a 5-foot par putt on the final hole for a 68 that also left him five shots behind.
The notorious south Florida wind finally arrived, and everyone said it would lead to some unpredictable golf. It got downright goofy at the end of the day.
It started with Pettersson and his five putts. It ended with Hamilton being taken to the television trailer after his round because a viewer reported what he thought was an infraction.
The TV viewer said Hamilton realigned his ball on the 11th green after having picked up his coin.
'I would never do that,' Hamilton said, and replays showed that he never adjusted his ball.
The only outside comment Hamilton could trust was the guy that came up to him as he headed to the 18th tee.
'This guy comes up and says, 'Hey, you've got a three-shot lead. Pettersson just five-putted,'' Hamilton said. 'You never think a guy is going to tell you that. I didn't know what to think. Maybe he had a bet with someone.'
Sure enough, the leaderboard showed Pettersson at 10 under, and the 26-year-old Swede dropped another shot on the par-5 17th to fall further behind.
'It was nice to get that extra shot,' Hamilton said of his 15-foot birdie putt.
Everything will help, considering it took Hamilton 17 years to get to this stage. A victory would open the door to marquee events like The Players Championship in two weeks, and give him an exemption for the next two years.
Hamilton, an All-American at Oklahoma in the 1980s, had played only a dozen PGA Tour events until he finally got his card at Q-school last year.
But he knows how to win, as does Jacobson.
Hamilton is coming off his best year on the Japan PGA Tour, winning four times. Jacobson won three times on the European tour.
'Winning breeds winning,' Hamilton said. 'It will help both of us.'
As for the wind?
That could make it anyone's game.
Davis Love III finished with a 70 and joined Tom Pernice and Aaron Baddeley at 8-under 208. Robert Allenby had a 67 and was among a half-dozen players another shot back.
And as Saturday proved, anything can happen.
'It could be difficult to protect a lead,' Hamilton said. 'Or you can expand your lead that much more.'
Riley is the only player in the final two groups with a PGA Tour victory. That came two years ago at the Reno-Tahoe Open, when the world's best players were at a World Golf Championship the same week.
'They've never won before,' Riley said. 'So there's going to be a little pressure on them.'
The wind finally showed up not long after Pettersson teed off, although it didn't seem to bother the stocky Swede. He made two 7-foot par putts, then holed a birdie putt from 45 feet on the par-3 third.
Hamilton made sure that Pettersson didn't have the Honda Classic all to himself.
After missing a 2-foot par putt on the second hole, Hamilton quickly closed the gap by running off four straight birdies, then pulled into a tie with a 30-foot birdie on the par-3 eighth.
Pettersson, the leader since opening with a 63 in the first round, showed signs of cracking when he missed 4-foot par putts on the 12th and 14th.
But nothing was quite as damaging as the 16th.
He ran his 40-foot birdie putt some 15 feet by the hole, then rapped his par putt 4 feet past the hole. From there, it was like watching instant replay until he finally tapped it for his triple bogey.
His confidence rattled, Pettersson pulled his wedge into a bunker and bogeyed the 17th.
Divots:@ David Toms and Joe Durant, the third group of the day, finished their round and were almost finished with lunch by the time the next twosome came to the 18th hole. The delay became obvious as Per-Ulrik Johansson lined up his 15-foot par putt - from behind the ball, then behind the hole, then behind the ball again. He adjusted his ball and looked at the line again. Then he removed his coin marker, backed up and squatted again to read the line. The good news is he made the par putt to finish at 2 under, 12 shots off the lead. ... Fred Couples, who had a 73 and was at 5-under 211, is playing in his 500th event on the PGA Tour. 'I'm not sure what kind of milestone that is, but it's a nice number,' he said. It goes to No. 501 next week. Couples said because his wife was willing to come to Orlando, he decided to play in the Bay Hill Invitational for the first time in three years.
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