"It's a wonderful test. I love being in the thick of it. I've had opportunities in years past [finishing second a record five times]. It's been so fun, even though it's been heartbreaking to come so close a number of times. But I feel better equipped than I've ever felt heading into the final round of a U.S. Open."
He'd better be, because there's a hungry pack circling around Lefty waiting for him to slip, ready to play the biggest round of their lives to take home the prize. Fellow Americans Hunter Mahan and Steve Stricker, along with Englishman Luke Donald, are a shot behind. Donald's double bogey on the final hole while Mickelson bogeyed cost him a piece of the lead.
They're at even par, while England's Justin Rose, second round co-leader Billy Horschel and South Africa's Charl Schwartzel stand at 1 over. Another shot back is Australian Jason Day, with American Rickie Fowler plus-3 after recording the day's best round, a 3-under 67.
Among that entire group, only Schwartzel, the 2011 Masters champ, has won a Major.
"Yeah, it feels good. It's exciting,'' said Mahan, who briefly held a piece of the lead, before back-to-back bogeys on 17 and 18 dropped him to 1-under for the day, even par for the tournament. "I feel like my game's been good for a while and this course suits me pretty well. It feels good to be in the hunt and be in contention."
That's the universal feeling, knowing the stakes and knowing that conquering Merion will be the ultimate challenge. "It's going to be tough," said Donald, who's been ranked No. 1 in the world at times despite his lack of success in the big ones. "The course is only going to get tougher.
"I don't have any adjustments to make. I feel like for the most part I've played really solid golf the last three rounds. Of course my goal is to win Majors. I've won a lot of tournaments around the world, but I would dearly love to win one of these."
Whoever succeeds on Sunday will surely have earned it. Winning an Open is special enough. Winning at Merion, where Bobby Jones and Ben Hogan made history, where Lee Trevino beat Jack Nicklaus in a 1971 playoff, where Australian David Graham fired a virtually perfect 67 the final day in 1981 to claim victory, will only add to the luster.
"I feel like I'm in great position," said Rose, another who held the lead earlier in the day. "If you would've said to me Thursday morning, 'This is where you're going to be entering Sunday,' I absolutely would've taken it. But I know it's going to be tough."
So who's going to win the U.S. Open? That's anyone guess, to be answered shortly.
Let the fun begin.