Jordan Spieth, trying to become the youngest US PGA Tour winner in 82 years, shared the lead after Saturday's completion of the storm-interrupted second round of the $6.5 million National.
The 19-year-old American, a former world amateur number one who turned professional last December, shot a five-under par 66 Friday to match countryman Roberto Castro for the lead on seven-under par 135 before play was stopped.
A total of 64 golfers were forced to finish their second rounds Saturday morning at Congressional Country Club, with several making charges but none able to equal the overnight leaders after 36 holes.
"I'm excited for what the weekend is going to bring," Spieth said.
Spieth, who turns 20 on July 27, would become the fourth-youngest winner on the all-time US tour list and the youngest tour champion since 1931, when Ralph Guldahl won the Santa Monica Open at three months younger than Spieth is now.
"It would be huge," Spieth said. "I can't really think about that at this point. It's only halfway through so there's a long way to go."
Spieth has earned special temporary tour membership for the remainder of the season after winning $919,079, all but clinching a 2014 tour berth. A victory would bring a PGA spot for two years and a berth in this year's playoffs.
"It has been a great dream come true this year," Spieth said. "I'm just free swinging. I can't be in the playoffs unless I win and that makes winning the number one goal... I don't have to worry about making x number of dollars."
First-round leader Castro fired a 69 on Friday to stay level with Spieth.
"A lot of confidence going into the weekend," Castro said. "I feel good about two rounds in the 60s. That means you've gotten the ball up and down and you're going to have to keep doing that."
Argentina's Andres Romero returned to the course Saturday morning and birdied the par-4 14th and 15th holes, capping a run of four birdies in a row to briefly share the lead before stumbling with a bogey at the par-5 16th.
The South American closed with back-to-back pars to complete a five-under par 66 second round and stand third on six-under 136, one stroke ahead of South Korean Lee Dong-Hwon, American Jason Kokrak and Belgium's Nicolas Colsaerts.
Colsaerts, this season's US PGA driving distance leader, was two-under with 11 holes remaining when play was halted on Friday.
He closed out the front nine with back-to-back birdies when he returned to the course on Saturday and added a birdie at the par-5 16th on his way to completing a bogey-free 68.
Lee, last year's PGA Qualifying Tournament winner, is fighting to keep his tour spot at 129th on the money list with $364,830. He fired a 66 on Friday.
"My goal is to retain my card and I'm fairly confident that I'll be able to gain my card back for next year," Lee said.
Lee, a two-time winner on the Japan Tour, shared eighth at New Orleans in April for his best result in 17 career PGA starts.
Kokrak birdied four of the eight holes he played Saturday, all on the front nine, to finish a round of 66. Kokrak sandwiched birdies at the third and fifth around a bogey and followed with birdies at the par-5 sixth and ninth holes.