Will Betts of Leechburg, Pa., north of Pittsburgh, fired an afternoon 66 on the North course - the best round of the day - and tied Sawin at 137. Chris Crawford, who is entering his junior year at Drexel, was next at 139.
Sawin, a graduate of the Haverford School who grew up playing golf at Merion, made his decision after winning the Stocker Cup Invitational last October in Carmel, Calif.
"That put me on the invitation lists for a lot of great tournaments, including the Sunnehanna, the Northeast Amateur, the Porter Cup," he said. "As the calendar was starting to build out, it just seemed like a really good year to step aside from my job and really explore what the right balance of competitive golf and grueling finances was for me.
"For the last seven years, I was working really hard all the time. It was a great experience, but I think I want to find something that allows me to play competitive golf a little more often."
His game looked good Wednesday. He eagled the 11th hole on the Old course in the morning that sparked a 4-under score of 31 on the back nine. He carded four birdies in the afternoon, including back-to-back tap-ins, and punched the ticket for his second U.S. Amateur.
"It's a long day, so you have to stay even-keeled through the highs and lows," Sawin said. "I just felt like I stayed in the moment, which is real important when you start off well. On the second 18, you're not getting ahead of yourself, just taking each shot as it comes."
Betts, who is entering his junior year at Hartford, recorded seven birdies in his afternoon round on the North course.
(Old course score listed first)
Will Betts, Leechburg, Pa. . . . 71-66-137
John Sawin, San Francisco . . . 68-69-137
Chris Crawford, Bensalem . . . 67-72-139
Henry Shimp, Charlotte, N.C. . . . 70-70-140
Isaiah Logue, Fairfield, Pa. . . . 71-69-140
x-David Denlinger, Lancaster . . . 71-70-140
Oliver White, Lower Gwynedd . . . 73-68-141
Dylan Newman, New Rochelle, N.Y. . . . 69-73-142
x–won playoff for final berth