Todd Demsey matched the course record of 9-under 63 to climb into second place at 16-under-par 200. Bart Bryant and Tyler Williamson are one stroke further back at minus-15.
Anderson stumbled out of the gate with a bogey at the first. He came back with an up-and-down birdie at the par-5 fourth. Anderson two-putted for birdie at the par-5 sixth at the Black Creek Club to get to minus-12.
The 33-year-old dropped in back-to-back birdies from the eighth, both from within 4 feet. Around the turn, he stumbled to another bogey at the 12th.
Anderson responded from that mistake in fine fashion. He two-putted for birdie at the par-5 15th and came back with another birdie at the very next hole.
The Californian made it three in a row when he dropped a sand-wedge within a foot of the cup for birdie on the 16th. Anderson closed his round with a birdie at the par-5 last to claim the overnight lead.
'Today was different than the others,' said Anderson. 'It didn't feel solid at all. I just hung in there all day. I knew I needed to step up a little to get back in the game.
'Obviously 66 is not horrible, but it wasn't exactly what I wanted it to be. Someone will go low early tomorrow and I'll just try to do one better.'
Demsey birdied the second from 8 feet out and two-putted for birdie on the fourth to get to minus-9. He then ran off three straight birdies from the sixth to jump up the leaderboard.
On the back side, he picked up his sixth birdie of his round at the 10th from 4 feet. He dropped in back-to-back birdies from the 14th, both within 6 feet, to get to 15 under.
Demsey stumbled to his lone bogey of the day at the par-3 17th. He erased that error by draining a 25-foot eagle putt on No. 18 to grab second place.
'I've been playing well for a few weeks, but I haven't gotten anything out of it,' said Demsey. 'Today was the first day where I got some good breaks. It is obviously my goal to win, but it is too early to think about that. This is my sixth year and I haven't won. I would have thought I would have won by now.'
Justin Bolli, who also carded a 63 to tie the course record first set by Bart Bryant last year and matched in the first round by Michael Long and Anderson, moved into a tie for fifth place at 14-under-par 202. He was joined there by John Connelly, Robin Freeman and Johnson Wagner.
Ben Bates, Mathew Goggin and Nick Watney are one stroke further back at minus-13.
Nationwide Tour rookie Matthew Jones, who shared the overnight lead with Jason Caron, posted an even-par 72. He stands in a tie for 12th at 12-under-par 204. Caron struggled to a 1-over 73 and is one stroke behind Jones at minus-11.