Second round leaderboard:
-8 L Donald (Eng), J Furyk (US) -7 G Ogilvy (Aus) -4 KJ Choi (S Kor) Selected others: -3 P Casey (Eng) +1 P Mickelson (US) +2 J Rose (Eng) +8 M Laird (Sco)
Donald is in the running to win the FedEx Cup series
Luke Donald is tied for the lead with Jim Furyk at the Tour Championship, with fellow Englishman Paul Casey also well placed after round two in Atlanta.
Donald continued his preparation for next week's Ryder Cup with a 66 to move to eight under alongside Furyk, with Australia's Geoff Ogilvy a shot back.
Casey shot 71 for three under after closing with three successive bogeys.
Phil Mickelson had a disappointing day with a 72 that left him one over, with England's Justin Rose on two over.
A $1.35m (£868,000) prize awaits the winner of this FedEx Cup finale, with the overall winner of the FedEx Cup series earning $10m (£6.4m).
That jackpot is guaranteed to be Casey's if he wins on Sunday, while should Donald triumph he can be denied the prize only if either of the current top two FedEx points leaders Matt Kuchar and Dustin Johnson finishes second, with both the Americans off the pace.
Furyk was again the most impressive of the US Ryder Cup players on show with six birdies in a 65, while there were mixed results for team-mates Steve Stricker (68), Bubba Watson (69), Hunter Mahan (71), Zach Johnson (72) and Jeff Overton (70).
After chipping in on the first hole Furyk went on to reach the turn in 33 and he overtook Donald by picking up more shots at the 11th, 14th and 15th.
But Donald matched the birdie on the long 15th, sank a 31-foot putt at the 16th and then got out of trouble on the two closing holes at East Lake.
The 32-year-old, without a victory on the US Tour since 2006, is delighted with his progress in pursuit of the mammoth $7.5m purse, the winner taking away $1.35m.
Casey struggled with his game during the second round in Atlanta
"It was another good day score-wise, and I'm in a great position, so it was nice to build off a solid first round and continue that," said Donald. who was especially pleased with his play around the greens.
"I hit the short game a little bit on the back side, which kind of kept my score together."
Casey meanwhile, headed straight to the practice ground after his errant finish and said: "I fought my swing and the course is so difficult that if you get on the wrong side of it you're going to pay the price.
"I really don't often go and hit golf balls after a round of golf, but I'm about to. It's that bad.
"I'll be calling Mr Kostis (coach Peter Kostis), saying please help. If I want to get back up there and challenge these guys, I'm going to have to get ahead of it."
Furyk had the best round of the day, however, revelling with a new putter reportedly bought for $30, and the 40-year-old stalwart is looking forward to recouping substantially more in prize money.
"Dangling a big carrot at the end obviously has gotten everyone's attention because that's what everyone is talking about," he said/
"The only thing I can really control is to go out and play good on the weekend and try to win the golf tournament.
"It's a lot of money and late on Sunday, if any of us have a chance to win, I'm sure it'll weigh on your mind.
"What did Zinger (Paul Azinger) say - the only thing that ever made him choke was money and major championships? But we're at the halfway point and on Saturday it's not going to be an issue."