The 65 tied the all-time 18-hole record for a U.S. Junior Amateur Championship, matching the mark set by J.C. Deacon at the Country Club of York in 1999.
Campbell birdied three of the first five holes, and recorded nine birdies overall on the 6,613-yard, par-71 course.
Vargas shot a 30 on the back nine, bettering the old Junior Amateur mark of 31 set by three previous competitors. He is making his fifth appearance in a U.S. Junior Amateur, a feat matched only by Jack Nicklaus and Travis Whisman.
2000 champion Matthew Rosenfeld, 17, of Plano, Texas, shot an opening 77 in his attempt to join Tiger Woods as the only player to successfully defend the U.S. Junior Amateur title.
After a second day of stroke play Wednesday, the U.S. Junior Amateur field will be reduced to 64 players for match play. Two rounds of match play will be played on Thursday and Friday. The semifinals and the championship final are scheduled for Saturday.
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