Gone is that ugly streak of being 0-for-42, as a professional, in golf's biggest events. Gone are questions about Mickelson's game and whether it could stand up to the scrutiny of a major championship.
He delivered a command performance to the very end, with two birdies on the final three holes for a 3-under 69 that gave him a one-stroke victory over Els.
The putt curled into the back of the hole, setting off an enormous cheer. Mickelson jumped and thrust his fists, then kissed his ball when he plucked it from the cup.
'Oh my God!' he said as he walked off the green and into the arms of his wife and three children.
Until Sunday, he was known as the best player to have never won a major.
Now, he's simply one of the best in the game.
His awesome skills were on full display along the back nine at Augusta National, and they had to be. Els was flawless, making two eagles in his round of 67 that looked as though it would be enough to get the green jacket he covets, and the third leg of the Grand Slam.
But Mickelson was more determined than ever.
He rattled off three straight birdies to stay in range, caught Els with a 15-foot birdie putt on the 16th and then had the stage to himself on No. 18.
Despite a half-dozen close calls in the majors, Mickelson had never come to the final hole with a share of the lead. He never had the final say.
On this day, he refused to let his chance get away.
He smartly played 3-wood off the tee to avoid the bunkers and hit his approach behind the hole. Mickelson got a huge break with Chris DiMarco blasted out of a greenside bunker and just beyond Mickelson's ball marker, giving him the line on the biggest putt of his life.
'I just couldn't believe that ball fell in there,' Mickelson said.
Before walking into the scoring hut to sign his card, Mickelson held daughter Sophia and said, 'Daddy won. Can you believe it?'
Mickelson, who shot a 31 on the back, finished at 9-under 279. Mike Weir, whose victory last year made him the first southpaw to win the Masters, slipped the green jacket on the most famous Lefty in golf.
It was a bitter end for Els, who now knows how Mickelson has felt all these years. The big South African did nothing wrong over the final 12 holes, salvaged four crucial pars along the way and it still wasn't enough.
'I think Phil deserved this one,' Els said. 'He won this one. He didn't lose it like some of his other ones. Full credit to him.'
K.J. Choi holed a 5-iron from 220 yards on the 11th hole for eagle, kept his hopes alive with a 40-foot birdie putt on the 13th but wound up with a 69, three shots behind.
Tiger Woods was long gone before the fireworks started. He made a double bogey - this third of the tournament - on the 13th hole and shot 71, leaving him 11 shots out of the lead in a tie for 22nd, his worst finish ever at the Masters.
Woods now has gone seven majors without winning, and he has played his last five over par.
But this Masters didn't need him to deliver the drama.
With aces and eagles, so many spectacular shots along the back nine that the gallery was out of breath, it came down to Mickelson and Els in a duel as good as any at a major championship.
Els, playing two groups ahead of Mickelson, beat him on the par 5s with an eagle and a birdie.
Mickelson answered with an approach to the dangerous 14th that grazed the cup for a tap-in birdie, and a 15-foot birdie on the par-3 16th, a hole that has haunted him in the past.
'Baby!' Mickelson said as he trotted off the green, tied for the lead with two holes to play.
Playing the final hole, Els hit into a bunker so deep he could only see the hazy sky. He blasted out and said, 'Be right!' and it stopped some 25 feet behind the cup. His birdie putt turned just left of the hole.
Els was on the practice green, preparing for a playoff, when he heard the loudest roar of the day.
Mickelson made the putt. Mickelson won the Masters.
'Having it be such a tough quest, struggle, journey ... it feels that much better,' Mickelson said.
He became only the fourth player to win the Masters on a birdie putt at No. 18.
Only two other players - Harry 'Lighthorse' Cooper (31) and MacDonald Smith (24) - had more PGA Tour victories than Mickelson's 22 without ever winning a major.
Some began to doubt it would ever happen, especially since Mickelson was coming off his worst season ever. A year ago, he nearly lost his wife, Amy, during a difficult birth of their first son.
He refused to start practicing until Jan. 1, determined to put last year behind him. Now, Mickelson can look forward to many more tries at majors, without the pressure of having to win his first.
'Get used to me, because I'm going to be back every year,' he told the Augusta National members in green jackets, just like the one finally draped over his shoulders.
It wasn't easy - not over the last 12 years, not over the last 12 holes.
Mickelson and DiMarco began the afternoon as co-leaders, but came running back to the field after a good start. Mickelson took two shots to get out of the bunker on No. 5 for double bogey, DiMarco sailed over the sixth green for a double bogey.
Suddenly, the Masters was as wild as ever.
Despite two sloppy bogeys out of bunkers, Els shot into the lead and took control with a 15-foot birdie putt on No. 7, then one of the purest shots of the day - a long iron that caught enough of the slope at No. 8 to feed down to 6 feet for an eagle.
That put the Big Easy in the lead, and set the stage for the typical high drama at Augusta National.
So much for the changes taking away all the excitement on the back. This was as thrilling a Sunday afternoon as there has ever been at the Masters.
Padraig Harrington made a hole-in-one on the par-3 16th and Kirk Triplett aced the same hole a few minutes later.
Sergio Garcia whet everyone's appetite by playing the final four holes in 4 under par - one of those an eagle from inside a foot on No. 15 - for a 31 on the back nine and a 66, the lowest score of this Masters.
Mickelson couldn't help but hear it all. First came the cheers for him - 'It's your year, Phil. Make it happen!' - one man shouted. Then came the roars from all corners of the course.
The last cheer was for him. That was a first.
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