Washington - World No 2 Jordan Spieth fired a four-under-par 66 on Friday to stand second in the clubhouse at the storm-hit PGA Tour Dean and Deluca Invitational.
The reigning US Open champion, who defends that title next month at Oakmont, waited out bad weather that delayed the start of the second round at Colonial for 5 1/2 hours.
"Really made the most of the round," said Spieth, a back-nine starter who birdied four of the first five holes after making the turn. "All in all, it was a fantastic (second) nine that we played."
American Webb Simpson fired a 67 to cling to the clubhouse lead at 8-under 132 with Spieth one shot adrift.
"It's only halfway done," Simpson said. "I've got a lot of work to do."
Darkness halted play with 61 of 121 players still on the course and needing to finish their second rounds Saturday morning.
American Bryce Molder birdied five of the first eight holes but a double-bogey at the 12th hole left him on nine-under, only one ahead of Simpson with four holes to finish.
Patrick Reed was level with Spieth at 7-under through eight holes, moving up with birdies at the first and fifth, while India's Anirban Lahiri was on 6-under after 11 holes.
Spieth has been trying to work his game into shape since a back-nine Sunday meltdown last month cost him a Masters title and he missed the cut earlier this month at the Players Championship.
A last-round fade cost him a title chance last week at the Byron Nelson Championship in his hometown event, but this nearby tournament could produce the boost he needs ahead of his defending the US Open crown.
"I would say (my confidence) is up there close if I want to have it 100 percent trust by major time," Spieth said. "It's creeping up. Big step up from last week. It's getting close.
"I feel very comfortable over the ball this week. I felt like we put in some good work from Sunday to Thursday."
Spieth began with a three-putt bogey at the 10th hole, answered with a three-foot birdie putt at the par-5 11th and birdied the par-3 13th, dropping his tee shot five feet from the cup.
After lipping out from 13 feet for a birdie at 15, Spieth three-putted for bogey at the par-3 16th.
"The greens were up and it just took me a little while to adjust," Spieth said.
Spieth blasted out of a greenside bunker to five feet at the par-5 first and made his birdie putt, then sank a 20-foot birdie putt at the par-4 second, an eight-foot birdie putt at the par-3 fourth and a 14-foot birdie putt at the fifth.
Simpson opened with a birdie, blasting out of a bunker and sinking a three-foot birdie putt, but took a bogey at the par-4 seventh when he couldn't duplicate the feat, missing a four-footer after escaping the sand.
"It was kind of a grind," Simpson said. "I had to get up-and-down a few more times today and guess out of the rough what the ball was going to do into the green, but it felt great. I managed my game and I think I only made one bogey and made a couple birdies coming in, so that was nice."
He answered with a 17-foot birdie at the par-3 eighth and took the lead on late birdies at 16, where his tee shot landed three feet from the cup, and 18, closing his day with a 14-foot putt to edge in front of Spieth.