DeMorat, who graduated from Liberty University last month, birdied the par-4 18th hole to force a three-way playoff which he won on the second hole at Woodmont Country Club in Rockville, MD on Monday.
There were 36-hole US Open qualifiers at 11 venues on Tuesday (NZT), one in England and 10 in the US, for what was essentially the last opportunity for more than 800 players to secure the 71 remaining places available at Shinnecock Hills.
But the 22-year-old's seven-under-par 64 earned him at 12-under total and a three-shot win at the Portland site, where four US Open spots were up for grabs.
Ultimate #toursauce move: Having your caddie pull the ball out of the hole after making eagle to punch your US Open ticket.
Beachlands' Ryan Fox has added to his already successful weekend by qualifying for the 2018 US Open Championship at Shinnecock Hills Golf Club this morning. "But I set some good goals at the start of the season and I will just keep working to achieve them".
By qualifying Scott, Baddeley and Herbert take the Australian contingent at this week's US Open to nine, including West Australian Jason Scrivener who also qualified to make his major championship debut.More news: Asus ROG gaming smartphone with 90Hz display refresh rate, overclocked CPU launched
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Qualifying means the 2013 Masters Champion will continue his 17-year long streak of competing in every major championship.
"It was certainly nice to continue the form from yesterday's round into today and I'm just very happy and hopefully it can continue for another week or so entering the US Open".
It's been a standout season so far for Herbert who has been banging on the door of a breakthrough professional victory recording two top-3 finishes on the European Tour and a T8 result on the Asian Tour and Japan Tour co-sanctioned Singapore Open that result sealing his spot at Carnoustie for The Open in July.
It will be Wilkinson's second US Open appearance after he finished tied for 61st two years ago at Oakmont Country Club.
Wilkinson, who plays the Web.Com Tour, was also successful in Sectional Qualifying in 2016.