Roberto Castro carded a 2-under 69 before play was suspended for rain on Friday to maintain a share of the lead at the AT&T National.
Jordan Spieth fired a 5-under 66 during his second round to meet Castro atop the leaderboard at 7-under-par 135.
"It was a great ball-striking day and, honestly, it came down to how well I was hitting my driver," said Spieth. "I felt comfortable working the ball both ways and I found a little groove when I was teeing the ball up. From there I had a lot of great opportunities to attack pins, play it on the safe side and it worked out for me."
D.H. Lee also shot a 66 to grab a share of third place with Andres Romero at 5-under.
Romero is 4-under through 13 holes and will finish his second round at Congressional Country Club's Blue Course when play resumes at 7:00 a.m. ET Saturday.
Cameron Tringale (67) and James Driscoll (69) are tied for fifth at 4-under 138.
Castro entered the day with a 2-stroke lead, but lost some of that cushion at the third with a 2-putt bogey after hitting his tee shot into a fairway bunker.
After parring the next four holes, he rolled in 25-foot birdie putt at the eighth to again reach 5-under and followed that with a short birdie putt at the ninth.
He would then par his next six holes before converting another short birdie effort at the 16th to move to 7-under. He parred his final two holes to stay there.
"It feels good to play two rounds under par," Castro said. "It's a very hard golf course."
Spieth, meanwhile, used a blistering front nine to meet Castro in a share of the lead.
His outward 31 began with a 26-foot birdie putt at the first, and he later converted back-to-back birdie efforts at the fifth and sixth to move to 5- under for the tournament.
Spieth then capped another pair of gains at the ninth with an 11-foot putt to grab a share of the lead.
He would par his next nine holes to remain tied atop the leaderboard.
Romero cruised through his outward nine with birdies at Nos. 3, 6 and 8 to make the turn at 4-under before tripping to a bogey at the 11th.
But he bounced right back with back-to-back birdies at the 12th and 13th to pull within two strokes of the lead prior to play being suspended.
NOTES: Spieth hit all 18 greens in regulation during his round. It was the first time he did that in 72 rounds on the PGA Tour ... Should Spieth go on to win, he would become the fourth-youngest winner on the PGA Tour since 1900 at 19 years, 11 months old. The youngest winners are Harry Cooper at 19 years, 4 days at the 1923 Galveston Open, Ralph Guldahl at 19 years, 8 months 1931 at the Santa Monica Open and Johnny McDermott at 19 years, 10 months at the 1911 U.S. Open ... Justin Hicks withdrew with a back injury during the second round ... The start of the third round is scheduled for approximately 10:50 a.m. ET in threesomes off split tees.