McLachlin, who will go for his first tour win on Sunday, stands at 17-under- par 199 after 54 holes. This is his first 54-hole lead on tour.
Kris Blanks fired a 5-under 67 Saturday to jump into a share of second place at minus-10, He was joined there by Matthew Jones (71), Scott Parel (70) and Jimmy Walker (68). Arjun Atwal, Scott Dunlap and Ian Leggatt are one stroke further back at 9-under-par 207.
McLachlin tripped to a bogey on the first, but recovered that stroke with a birdie on the par-3 fourth. After three straight pars, McLachlin drained a 12-foot birdie putt on eight to move to 14 under.
The Hawaii native dropped in a 4-foot birdie putt on the 10th at Pete Dye Golf Club to push his lead to four.
McLachlin parred his next four as his lead grew. He moved to 16 under with a birdie at the 15th.
The 28 year old knocked his third to five feet at the par-5 17th and converted that for birdie and a seven-shot lead. McLachlin saved par from 4 feet at the last to maintain that cushion.
'I've been putting in a lot of hard work and it is finally paying off,' McLachlin stated. 'I didn't hit it very good today, but the other parts of my game really came through. I chipped and putted real well. It's nice to see the payoff from all the hard work I've put in.'
McLachlin is playing in his first event on the Nationwide Tour this season. He missed out on the PGA TOUR's FedExCup playoffs, ranking 156th on the money list and 158th on the FedExCup points list.
Blanks carded just one birdie on the front nine, but ran off five birdies in a seven-hole span from the 11th to jump to 11 under. However, he bogeyed the last to end in a share of second.
Jones was even-par for his round after 13 holes with three birdies and three bogeys. He got to 10 under with a birdie on the 17th.
Parel birdied No. 3, but bogeyed three of the next five. Birdies on the 10th and 13th got him back to even-par for his round. He also birdied 14, 15 and 17 to get to 11-under. Like Blanks, Parel bogeyed the last to end at minus-10.
After a bogey on the first, Walker eagled the second, then birdied two of the next four holes to jump to minus-9. He parred 11 straight before a birdie at the last gave him a share of second.
Jason Schultz used a 67 to move into a share of ninth at 8-under-par 208. He stands alongside Justin Hicks, Edward Loar, Justin Smith and Kyle Thompson.