England's Brian Davis and South African Louis Oosthuizen shared the clubhouse lead on Friday as darkness stopped play in the second round of the rain-hit Houston Open.
Seventy players were still on the Redstone course when darkness fell, the legacy of thunderstorms that caused delays on Thursday.
Davis and Oosthuizen were in the clubhouse on 11-under par 133, Davis completing a first-round 68 on Friday morning and following up with 65.
Oosthuizen added a second-round 66 to his opening 67.
Jeff Maggert was at 10-under with eight holes remaining when play was halted.
Defending champion Phil Mickelson, who had seized a share of the first-round lead Friday morning as he wrapped up a 65, shot a second-round 70 to head a group in the clubhouse on nine-under 135. He was joined by J.B. Holmes (67), Tommy Gainey (67), and England's Greg Owen (69).
Three-time major champion Ernie Els, who needs a victory to book a berth at the Masters next week, carded a second-round 69 for 139.
Davis played a total of 32 holes on Friday, but looked anything but tired as he made seven birdies without a bogey in his second round.
The 37-year-old Englishman said he made changes in his life after the death of his father, Robert, from cancer last year.
"I think I'm more prepared going forward now this year," he said.
Davis changed his caddie and his swing, and also worked with sports psychologist Bob Winters on managing his time.
"I really struggle when my kids say, 'Can we do this?' and I should be practising," Davis said. "It's hard to juggle that around. You've got to give yourself some time as well."
Davis missed the cut in three of his first four starts, but said he thought things were coming around.
"It's one of them things, you've got to stay the course and keep at it," Davis said.
Like Els, Davis must win here to earn an invitation to the Masters next week.
"Obviously, I'm well aware that I need to start winning," said Davis, who has never won on the US tour. "It's one of those things where you can't force it. You've just got to keep putting yourself in position."
Oosthuizen, the 2010 British Open champion, has made some changes to his swing, and returned to the driver he used in his St. Andrews triumph.
"I hit it well at the Open in 2010, and I feel like I'm very close to hitting it like I did there," Oosthuizen said. "Swing-wise, I feel confident."
Mickelson was rolling along nicely with birdies at 10 and 15 after teeing off on 10 in the second round, when he bogeyed the par-three 16th. He made two more birdies, but closed with a bogey at the par-three ninth.
"I played pretty well the second round, but I didn't get the score that I had hoped," Mickelson said. "I've got to light it up this weekend."