Stars and Stripes for Stadler on Independence Day
Kevin Stadler tees off during the 78th Masters Golf Tournament at Augusta National Golf Club on April 12, 2014 in Augusta, Georgia - by Emmanuel Dunand
The burly 34-year-old from Reno, Nevada, backed up his opening day 64 with a three-under 68 to stand alone on 10-under-par and in command at the halfway point of a tournament founded in 1906.
Victor Riu gave home fans real hope of a first French champion since Thomas Levet in 2011 with a 67 to take second spot on seven-under, while Germany's Marcel Siem, who needs a top ten finish this weekend to qualify for the Open on July 17 at Hoylake, was two shots further back on five-under.
Another solid round by Stadler, that featured four front-nine birdies and two more down the home stretch, was only marred by a double bogey at the 18th which denied the player, who uses a long putter, an even bigger lead.
"I tried to get a little too much out of my third shot on 18 and didn't have the best of lies so I had to hit the shot perfectly and just tried to get a little too steep on it and off it came into the deep stuff," Stadler said in reference to his final hole blip.
"Not exactly how I planned to finish the day but overall it was another good day, so it's all good.
"I definitely didn't expect to be 10 under after two days but I played well in the Pro-Am and I'm obviously very pleased with 10-under through two days.
"It's just a really good golf course, greens are great and I'm certainly enjoying it so far."
- 'Almost unbelievable' -
Stadler, who won his second professional title in February when he lifted the Phoenix Open crown, has so far been better known as the son of 13-time PGA winner Craig 'the Walrus' Stadler who won the 1982 Masters in a play-off.
In April, they became the first father-and-son duo to play at the Masters where Kevin finished in a tie for eighth on his debut at Augusta.
"Overall it's a very good day, I don't know if the lead will hold up, there's still half a day to go and the weather's supposed to get nasty the next couple days so we'll have to wait and see," Stadler added.
The only victory to date for the 29-year-old Riu, from nearby Saint-Nom-la-Breteche, was on the Challenge Tour in 2013 when he won the Swiss Challenge by three shots.
"It's really another great day for this second round," said Riu.
"Just one bad note, the bogey I conceded on the 18th hole but for the rest of my game everything functioned really well.
"After a first round that was more or less mediocre, to find myself in the upper part of the leaderboard is almost unbelievable."
Defending champion Graeme McDowell of Northern Ireland finished strongly with birdies at the 11th and 16th to finish his second round on three-under-par and seven shots off the lead.
US Open champion Martin Kaymer shot a one-under-par 70 and made the cut but now needs to make up nine shots on Stadler if he is to win a second French Open after triumphing on the Albatross course in 2009.