World number one Dustin Johnson clung to a two-shot lead halfway through the final round at the Masters on Sunday as a dogged Cameron Smith ensured it would be far from a one-man procession at Augusta National.
Johnson teed off with a four-shot advantage but after successive bogeys at the fourth and fifth holes his lead was briefly down to one with Im Sung-jae then hot on his heels.
The super-talented American, with just one major title for all his ability, looked as calm as ever on the outside, but inside his stomach must have been churning.
Yet at the 180-yard par-three sixth, he took dead aim from on top of the hill, and his ball never looked like ending anywhere but near the pin.
It settled seven feet away and he converted the birdie, while Im bogeyed the same hole for a two-shot swing.
Johnson later had a two-putt birdie at the par-five eighth and turned at 17 under par, but Australian Smith, in the group ahead, was not ready to give up the fight.
He played a superb if slightly lucky approach shot at the par-four ninth, where his ball barely skirted a bunker before taking a fortuitous roll down the slope to set up a four-foot birdie.
That took Smith to 15-under at the turn in his quest to become the second from his nation to earn a Green Jacket after Adam Scott.
Smith picked up three shots on the front nine, with four birdies and one bogey.
South Korean Im was four shots back, probably the only other player with any chance of winning.
Earlier, Johnson teed off four shots ahead of Smith, Im and Mexican Abraham Ancer.
Johnson made a regulation par at the first, but almost butchered the par-five second, chunking a pitch shot into a bunker, from where he had to get up-and-down just to save par.
Johnson, a perennial contender in the biggest tournaments, would double his major haul with victory, his only previous triumph coming at the 2016 U.S. Open.
Tee times on Sunday were delayed 10 minutes after fog enveloped the course, and it had not totally cleared when the leaders set off at 9.39 am local time.
But the sun was already piercing through and the fog quickly cleared.
The wind also picked up a bit for the first time all week, perhaps setting the stage for back-nine drama, though the course will continue to play relatively easy given the soft conditions after heavy rain in the week.
Officials have also dispensed with some traditional Sunday pin positions, which have often been placed in the easiest spots to facilitate birdie chances, particularly on the back nine.
But due perhaps to the soft conditions, which allow players to attack with their approach shots in the knowledge the ball will stop quickly, officials have mixed it up this year.
For example, the easy hole location on the par-three 16th has been dispensed with this year and a much tougher location on the back right-hand side of the green, just four yards from the fringe, has been placed.
However, the hole at the par-five 15th is in a relatively generous location, in the back-middle of the green, which should allow players to pepper the pin with their second shots and lead to good eagle opportunities.