Kevin Streelman and Charley Hoffman were a stroke behind Davis at 66, while Johnson Wagner also shot 67. U.S. Open champion Webb Simpson led a large group at 68.
Day and Leishman can't make history for their country at the RBC Heritage only enhance it. Several Aussies have won at Harbour Town, including Graham Marsh in 1977 and Greg Norman 11 years later. Aaron Baddeley was the last Australian to take the champion's tartan jacket in 2006.
"For a population that I think is around 23 million people in Australia, and the last time I checked the land size is a little bit bigger than North America," Day says. "We do pretty well in sports."
That's been apparent on the PGA Tour in recent weeks.
Scott, Day and Leishman were all in hunt at Augusta National on the back nine until Scott, the most experienced of the Aussie trio, rose up at the end and beat Angel Cabrera in a playoff. Day finished third and Leishman tied for fourth, meaning all three are already qualified to return for the 2014 Masters.
There's a lot of work ahead before then, Day said, especially with Davis playing Harbour Town as well as anyone in recent years.
Davis was toe-to-toe with Furyk three year ago until he brushed a loose reed with his club in the marsh area left of the 18th green. Davis immediately called the infraction, which essentially gave Furyk the crown.
Davis, never better than second on the PGA Tour, still gets stopped at country clubs and airports by admirers of his honest act on the course in a situation where victory would've made Davis' career much smoother.
In Kapolei, Hawaii, defending champion Ai Miyazato had five birdies in a late six-hole stretch at breezy Ko Olina to open a two-stroke lead midway through the second round of the LPGA Lotte Championship.
The Japanese star, a nine-time winner on the LPGA Tour, shot a 4-under 68 to reach 9-under 135.
Hyo Joo Kim, the 17-year-old South Korean player who played in a group with 17-year-old Ariya Jutanugarn and 15-year-old New Zealand amateur Lydia Ko, was second along with Hee Kyung Seo and late starter Suzann Pettersen. Kim shot a 71, and Seo had a 72
Local favorite Michelle Wie followed her opening 70 with a 76 to put her in position to miss the cut.
RBC Heritage leaderboard
Brian Davis -6
Kevin Streelman -5
Charley Hoffman -5
Marc Leishman -4
Jason Day -4
Johnson Wagner -4