Fredrik Jacobson posted a 64 to finish alone in second place at 8-under-par 132. Paul Goydos was one shot further back at 7-under-par 133 after a round of 66.
The 32-year-old recovered with a birdie at the par-5 16th and rolled in a 9-foot putt for a birdie at the par-4 17th to make the turn at 10-under par.
'I felt like it is difficult to come back after shooting a low round and the next day your expectations are so high that sometimes a round can get away from you,' said Leonard. 'Today I really did a good job of not worrying so much about the score but hitting the shots that I needed to hit.'
Leonard kept on rolling on the front side with a birdie at the par-5 third after his third shot stopped within 5 feet of the hole. He parred his next two holes and hit his second shot from the rough inside 7 feet at the par-4 sixth for another birdie.
Leonard added a birdie at the par-4 seventh and parred his way in to carry a comfortable advantage into the weekend.
'I have to stay in the present, not worrying about scoring or what is going on, just trying to execute the golf shots,' said Leonard, who won the Bob Hope Chrysler Classic earlier this season. 'I did it very well today. I see no reason not to continue with that this weekend.'
Jacobson jumped out of the gate on Friday with birdies on each of his first three holes. The Swede continued his climb up the leaderboard with back-to-back birdies from the 12th and closed with a birdie at the 18th.
'I haven't really worried about what the scoring was or about closing in on the lead,' said Jacobson. 'I just try to do what I did yesterday. I try to work on my own game. That led up to a good score that I am happy about.'
Tom Pernice, Jr., Matt Gogel, Heath Slocum and Roland Thatcher share fourth place at 6-under-par 134. Davis Love III, Kirk Triplett and Richard S. Johnson were one shot further back at 4-under-par 136.
Defending champion David Toms managed a 1-over 71 to finish well off the pace in a group at 1-under-par 139 that features Nick Price and Brad Faxon.
The 36-hole cut fell at 2-over-par 142 with 74 players qualifying for the weekend. Among those who didn't make the grade were Hal Sutton, Loren Roberts, Jeff Maggert and last week's winner Kenny Perry.