"I've got to putt better," said Williamson, who iced his right shoulder after the round. "I've got to be more confident with my stroke."
Lonard followed up an opening 67 with the 70 on Friday. At one point, he was 10 under with a four-shot lead, but that was before bogeys on 15, 17 and 18.
"The first one was just up against the face and I had to chip it out sideways," Lonard said. "The one on 18 was about 80 to 100 yards off-line, so I suppose I deserve that one. You've got to hit fairways, that's the name of the game."
Defending champ Nick Watney (67) was two strokes back at 6 under.
"I played a nice round to get back in the tournament," Watney said. "Hopefully I'll keep it going on the weekend."
Eighty-one players made the cut at even-par 144. Under the tour's revised cut policy, the field will be cut to the low 70 players and ties after the third round.
