Defending champion Vijay Singh posted a 68 in the second round and shares fifth place with Paul Stankowski, who carded a 6-under 66. The pair is knotted at 9-under-par 135.
A number of players returned to the course Friday to complete their first rounds. The final groups, including Kuehne, completed their second rounds in darkness but every group finished.
Couples started quickly on Friday with a 20-foot birdie at the par-5 opening hole at Redstone Golf Club. He wedged his approach to 10 feet to set up birdie at No. 4 but dropped a shot at the par-3 fifth when he missed the green and two-putted.
Couples closed his nine with back-to-back birdies at eight and nine but he dropped another shot to par around the turn. He rebounded with a 25-footer for birdie at 13 and a 20-footer for birdie at 17 to grab his first piece of a 36-hole lead on tour since the 1998 Memorial.
'It was a great round,' said Couples, the 1992 Masters champion. 'I played a round of golf where I didn't want to make a mistake or try not to and it worked out great. I am very thrilled with 68.'
Calcavecchia was flawless on Friday. He opened his round with three birdies in his first four holes before parring out the remainder of his front nine to finish at 3-under 32.
On the second nine, Calcavecchia once again started quickly. He sank a 20-foot birdie putt at the 11th and followed with a tap-in birdie at the par-5 12th. Calcavecchia parred No. 13 but once again racked up back-to-back birdies, this time at 14 and 15 to polish off his round of 7-under-par 65.
'I think obviously the guys that you have on the top of the leaderboard are playing just that much better,' said Calcavecchia, who had knee surgery at the beginning of this season. 'The course is so fair and the wind is not swirling around where one minute it is blowing 20 miles an hour and next minute it is stopping where it's got everybody baffled. It is as fair as it is going to get right now.'
Calcavecchia might be undergoing his second career resurgence. In 2001, Calcavecchia won the Phoenix Open in record fashion and made the United States Ryder Cup team, but in 2002, Calcavecchia earned only three top-10 finishes.
'I said I will win a tournament this year. I honestly felt like it,' said Calcavecchia. 'I wasn't just making it up just saying, sure, I am going to win a tournament. I honestly feel like I am. I will be in good shape this week going into Saturday. Now I have got to go out and I am narrowing in on it, but it's been a couple of years, so I am ready to jump into that winner's category again.'
Kuehne, the 1998 U.S. Amateur champion, began his round on No. 10 and collected five birdies on his first nine holes. He birdied one and four and in the darkness, Kuehne holed a 35-foot birdie putt at the par-5 ninth to set a new tournament course record with an 8-under 64.
'I am playing really well and I am pleased with my game,' said Kuehne, who entered the field this week thanks to a top-10 finish in his last event, the BellSouth Classic. 'I think my golf game is pretty good right now. I am just trying to basically get myself in a position where I can do something on the weekend.'
David Toms, the 2001 PGA Champion, shot a 66 on Friday and is part of a group at 8-under-par 136. David Sutherland (67), David Peoples (70), Tom Pernice, Jr. (70) and Stuart Appleby (70) joined Toms in a tie for seventh, three shots off the pace.
The 36-hole cut fell at 3-under-par 141, the lowest at the Houston Open since 1993 and 70 players advanced to the weekend, which is the lowest total of the season.
Among the notable players to miss the cut were Matt Kuchar (143), U.S. Ryder Cup captain Hal Sutton (148) and young Australian Adam Scott, who also posted a two-day total of 148.