The battle for the 113th title enters its final day with a number of players in contention but none more of a sentimental favorite than Phil Mickelson, who will play the East Course on his 43d birthday with a chance to win his first Open after five runner-up finishes.
Mickelson shot an even-par 70 on Saturday and stood at 1-under 209, the only player under par for three rounds. He holds a 1-stroke lead over three players - Hunter Mahan, Charl Schwartzel, and 46-year-old Steve Stricker - and is up by 2 over Justin Rose, Luke Donald, and Billy Horschel, who shared the 36-hole lead with Mickelson.
None of Mickelson's closest pursuers has ever won the U.S. Open, either.
The legend of Mickelson, a four-time major champion whose best shot at winning an Open came in 2006 at Winged Foot in the New York suburbs, shows how difficult it is to win just one Open. Much of the difficulty this year has to do with Merion, the U.S. Golf Association's setup, and the experience of the previous three days.
After three rounds at Merion, contestants feel added pressure knowing they must be precise with tee shots and approaches or else suffer the consequences of 4- and 5-inch-high rough.
On the final day of an Open, players tend to discard their carefully crafted game plan and start trying shots that might work in a regular PGA Tour event, but not in a U.S. Open. If they miss a few four- and five-foot putts, they start second-guessing their reads of the slick greens, changing their mind in the middle of their putting stroke. With all this, scores are apt to soar.
Webb Simpson kept his wits about him last year at the Olympic Club in San Francisco, firing a 2-under-par 68 in the final round to win the championship by 1 stroke.
"It was a crazy feeling on the back nine there with all that pressure, but it was so much fun at the same time," Simpson said last month. "It was a good kind of nervous."
However, most Open final days are a survival test. Graeme McDowell shot a 3-over 74 in the final round of the 2010 Open at Pebble Beach and won. Lucas Glover had a 73 (3-over) and won at Bethpage on Long Island in 2009. Tiger Woods carded a 2-over 73 and found himself in a playoff at Torrey Pines near San Diego with Rocco Mediate (71) in 2008, which Woods won.
The last time the Open was contested at Merion in 1981, David Graham played as pristine a final round as was ever seen in the championship. Graham missed one fairway the entire day and hit 15 greens. On the three greens he did miss, he used the putter from the fringe.
Mickelson showed some moxie on Saturday after a disappointing front nine that saw him repeatedly burn the edge of the cup on makeable birdie putts while carding two bogeys. But he birdied three holes on the back nine, including the long par-3 17th where he sank a 10-footer, to grab the lead, though his margin went from 2 strokes to 1 after a bogey at 18.
"I thought that I played better again than the score dictated, but this is a really fun challenge," Mickelson said. "It is a hard challenge but it is a lot of fun. Every shot requires such great focus because the penalty can come up and bite you so quickly here. It's just a very penalizing golf course. But there are birdie holes out there."
Should Sunday's competition end in a tie, an 18-hole playoff will be conducted beginning at noon Monday. Two of the last three Opens held at Merion have ended in playoffs, with Ben Hogan defeating Lloyd Mangrum and George Fazio in 1950, and Lee Trevino outlasting Jack Nicklaus in 1971.
The Open may end in a tie. It may wind up with the crowds saluting Mickelson on his first Open victory. Or Stricker on the first major of his career. Or a young player, or even 19-year-old amateur Michael Kim, who is 5 shots back.
But it will be a fight, a grind, and in some fashion, a quality winner will emerge.
Contact Joe Juliano at email@example.com. Follow on Twitter @JoeJulesInq.