On his 20th effort, the 43-year-old finally cracked the links code and in doing so became the oldest winner of the Claret Jug since Roberto De Vicenzo lifted the prize in 1967. Because of his history with seaside golf, and because of what this meant to his standing in the game, it can be legitimately asked if the Open has ever witnessed a better final back nine than Mickelson's 32.
While everyone else had been cowed into caution by Muirfield's glorious menace, the game's gunslinger took it on - and stood proudly, in every sense of the expression. Mickelson became the first to complete the Scottish Open-Open double, this replicating his feat of winning the Masters in 2006 having won on tour the week before.
So the old one-two are back on top and Tiger Woods is rather frantically looking over his shoulder. In the past decade Woods has won six majors and Mickelson five. Lefty leapfrogs Rory McIlroy in the rankings with only his nemesis blocking him for the world No1 spot he has remarkably yet to fill.
He could do so at the USPGA in three weeks' time and then, after his beloved Masters, it would be all roads to Pinehurst.
But for now golf will look back on an enthralling major. So much for Poulter claiming after his first round that the greens needed only windmills and clowns' faces. He decided to play some crazy golf and a few hours later Mickelson followed him. By this stage, Westwood had forsaken his lead with a front nine that he will want to forget very soon.
In truth, Westwood had not located his A-game all week.
While Ian Baker-Finch, the 1991 Open champion, has switched on the light in just one putting session with Westwood, his work with the long-game coach Sean Foley will obviously take longer. The Canadian had urged Westwood to put the ball further forward in his stance but here he reverted to old ways.
Questions will be asked if he will ever win a major and with eight top-threes in his past 21 attempts his image as golf's "nearly man" will obviously gain weight. Westwood will not worry. The work will carry on.
As it will for Woods. His recent weekend record in majors is becoming one of the more startling of golfing stats. Thanks to a 72, 74 here he is 23-over for his past 14 weekend rounds. He looms in contention but when everyone expects him to put his foot on the gas his game inexplicably squeals into reverse.
His pursuit of Jack Nicklaus' 18 majors now seems more unlikely than ever.
Scott will merely wonder about another let-down on the back nine of an Open. Poulter, meanwhile, will grab his usual wheelbarrow of optimism and rightly, too. He popped in his Ryder Cup eyes when the going got tough and produced exactly when he had to.
But essentially, this was all about Mickelson, the golfer who no longer just thrills but kills.
Jack Nicklaus, Gary Player, Tom Watson, Lee Trevino, Sir Nick Faldo, Ernie Els ... Phil Mickelson fits Muirfield perfectly.
