Lefty only made it look that easy.
Having just gotten back into a share of the lead after playing partner Rod Pampling's bogey at No. 17, Mickelson hit his final drive Sunday well left -- into heavy rough and under the trees 140 yards from the hole. Pampling then drove into the middle of the fairway.
Play it safe and chip back into the fairway? Not Mickelson, who is second to Tiger Woods in the world rankings.
"I didn't see that option," he said. "If there is at all a chance, I'm going for it. ... You have to take some risks to win."
Mickelson hit a wedge shot under one tree and over another, the ball clipping branches while headed sky-high -- "it just came off perfectly," he said. But Mickelson couldn't see it through the trees, so he jogged into an opening just in time to see the ball fall back to earth near the flag.
"That's what No. 2s in the world do," Pampling said. "Those guys make those kinds of shots."
Pampling left his approach 38 feet away and his second putt went in after Mickelson had already made his birdie -- actually from 9 feet, but no need quibbling over a one-foot difference after that shot Mickelson called "probably top five" in his career.
"Just lucky," he said, with a smile. "I'm as surprised as anybody I was able to make a 3 from over there."
The miracle birdie closed out a round of 2-under 68 that got Mickelson to 14-under 266, a stroke better than Pampling (68) and Tim Clark (66) for his second victory at Colonial. Stephen Ames (70) finished fourth at 269, a stroke ahead of Ben Crane (67).
It was the 34th career victory for Mickelson, who also won the Northern Trust Open in February and is the only person on the PGA Tour with multiple victories in each of the past five seasons.
"I felt like before I came here that this tournament needed to be the start of my run to the U.S. Open," Mickelson said.
Pampling had birdies at Nos. 6, 7 and 9 to make the turn at 14 under and with a two-stroke advantage over Mickelson, who like the day before fell behind before regaining the lead on his final putt.
After driving into the right rough at the 394-yard 6th hole, Mickelson's second shot hit a tree branch and ricocheted left into the fairway, though he managed to save par after hitting the third shot within 3 1/2 feet. But Pampling made a 48-foot birdie putt off the fringe, after coming out of his stance once because of a noisy spectator.
Then at No. 7, Pampling outdrove Mickelson by 60 yards and made a 7-foot birdie to get to 13 under, before an approach to 4 feet at No. 9.
"He looked like he was in control," Mickelson said. "I was obviously very fortunate to come out on top."
Mickelson got back within a stroke after getting on the green at the 611-yard 11th in two, then two-putting from 33 feet. Pampling, the Australian native who lives in nearby Flower Mound and gets to play Colonial often, had a 13-foot birdie chance stop right by the hole.
They kept matching pars after that -- until No. 17, when Pampling drove way right toward a ditch. He had to take a penalty stroke after a drop -- though that put his ball where it could be seen rather than buried in heavy rough at the edge of a concrete gully. He managed to get the approach shot into a bunker, then blasted to 4 feet. That came after Mickelson had two-putted from 28 feet for par.
"At times I got nervy, I was trying to relax, do breathing and focused on what I have to do. I was fine out there," Pampling said. "It was bad swing on 17. It was the only one I was disappointed in."
At the par-3 16th, Pampling's hand slipped on his tee shot and the ball wound up in a greenside bunker. But he blasted within 9 feet and saved par.
Pampling still may have done enough to get into the top 50 for a spot in the U.S. Open.
Clark, who has never won on the PGA Tour, had birdies at Nos. 16 and 17 to get to 13 under.
As Mickleson and Pampling were finishing No. 17, Clark's 14-foot birdie chance at the closing hole curled just short. He finished second for the sixth time in his career.
"I wasn't trying to force anything. I was playing the course the way I did the first few days," Clark said. "I made some good shots coming in and made a few putts. It was disappointing I left 18 short."
Notes: Mickelson earned $1.098 million, nearly double the $594,000 check he got for winning the last Colonial eight years ago, and surpassed $49 million in career earnings. ... Geoff Ogilvy, the No. 7-ranked player, followed an opening 72 with three subpar rounds and finished tied for seventh at 273. Ogilvy and Mickelson were the only of the five top-10 players in the field to make the cut. Jeff Quinney qualified for the U.S. Open by moving into the top 10 on the PGA Tour money list. He missed the cut his only U.S. Open, in 2001 when playing as the winner of the U.S. Amateur.