He might just be peaking a touch too early.
Six days before the British Open starts at Royal Birkdale, where he lifted the claret jug for a second time in 2008, Harrington was in a three-way share of first place at the Scottish Open after a bogey-free 4-under 68 in the second round on Friday.
''Maybe I'll have blown it all before next week,'' the easy-going Irishman said.
A three-time major champion, the 45-year-old Harrington is playing with a new-found freedom after concluding that he has already created a golfing ''legacy.'' He is also fit to play - amazingly, in his opinion - despite being struck in the left elbow by the club of an amateur he was teaching at a clinic last month. He initially feared the freak incident would end his career.
After a chaotic end to his first round when he chipped in from the back of the 17th green after saving par with a 25-yard putt on No. 16, Harrington kept it simple at Dundonald Links by making birdies on two of the par fives and birdieing two other holes from 7-iron approaches.
''Today was just boring,'' he said. ''No stress.''
It sums up his current approach to golf.
''When I came on tour, I played with some of the elder statesmen and I used to watch them fighting it, and at times I asked them, 'Why are you fighting it?''' Harrington said.
''And they say, 'Well, if I can win one more tournament...' And I was thinking, you've already done everything you're going to do, one more tournament is not going to change it. I'd hate to be that guy ... I've kind of come to the conclusion that I've pretty much done what I've done in the game of golf.''
It may just be a defense mechanism to relieve pressure, especially leading into a British Open where he'll be under more scrutiny than usual after what he did the last time golf's oldest major was held at Birkdale. He won by four shots on the back of a brilliant back nine in his final-round 69, and retained his title.
And he sees no reason why he can't win at the northwest England venue again.
''I can't tell you it's going to happen next week,'' Harrington said about winning again. ''But it will happen, just like winning in Portugal there six months ago; winning at Honda (Classic) the year before. I will throw these in, sometimes maybe out of the blue.''
Harrington said he has stopped beating himself up about his putting, which was the worst part of his game.
Also key to his recent revival has been a change to his swing. To protect his back, Harrington takes his left foot off the ground and steps forward after hitting the ball, in a kind of walk-on follow routine.
It looks funny but is getting results at the Scottish Open.