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The question was how would life be without Tiger Woods? The answer was provided by an Irishman who has played two of the greatest final nines in championship history to take The Open Championship and now the USPGA.
So superior and dominant was his play that there can be no asterisk against either triumph just because Woods was not in the field.
On the final holes at Birkdale he struck one flawless shot after another and at Oakland Hills he had a chance to put his case as the second best player in the world.
After a morning 66 when he broke the back of the course with birdies from the 13th to the 16th he was tied with his Ryder Cup team mate Sergio Garcia.
Harrington's first major championship had come at Garcia's expense at Carnoustie last year in a playoff and one wonders how their careers would have evolved had the result been reversed.
Harrington had double bogeyed the final hole there (making a brilliant up and down for the six) and to lose that way may have left a scar from which he was unable to recover.
At the turn there were four with a chance. Ben Curtis and Henrik Stensen were both a couple under par, two ahead of Harrington and one behind Garcia.
Stensen finished his hopes with a six on the par five 12th but Curtis was contending until the 17th when a fine tee shot ran long and into the ugly veranda of long grass at the back of the long par three.
Harrington birdied the 10th after a pair of perfect shots, got up and in for another birdie from over the par five and then he made a two at the par-three 13th.
Garcia meanwhile was making par after par after his brilliant birdie, eagle start and after Harrington hit long from the rough at the 14th and made a bogey Garcia had the lead by a shot and the match was on.
He hit the hole with a brilliant middle iron into the 15th hole and Harrington replied with a fine short iron from much closer after a more aggressive tee shot.
They both missed what perhaps they should have holed and faced three of the most difficult holes in championship golf. Only the three holes they duelled over at Carnoustie a year ago are noticeably harder.
Again Harrington took a longer club off the 16th and he left himself with a much shorter shot over the lake to the cup cut way back in the right corner of the green.
Garcia, with almost 180 yards to go, got his body ahead of his arms and that is a killer mistake going into the wind over the water. He made it over, just, but not by enough to stop it falling back into the lake.
Harrington with only an eight iron in hand pulled left into the sand but after Garcia had pitched his fourth shot to five feet, he blew a brave sand wedge from the sand to 12 feet and holed the curling putt for the par.
Garcia holed on top of Harrington and they moved to the long short hole and took five irons.
Going first, Harrington flew what looked to be the shot of the day on that hole within ten feet but Garcia answered with an awesome iron that finished only