He has never lost a PGA Tour event when he had at least a share of the 54-hole lead.
Reed made three bogeys in a seven-hole stretch in the middle of his round and salvaged an even-par 71, giving him a two-shot lead over Seung-yul Noh, Freddie Jacobson and Marc Leishman going into the final round.
He was at 6-under 207.
Reed will try to become the only player with four PGA Tour victories in the last year, and history is on his side. He won the Wyndham Championship when tied for the lead going into Sunday, and he converted a seven-shot lead at the Humana Challenge and a two-shot lead at Doral into victories.
Even without Tiger Woods boosting the energy at Congressional, and a leaderboard in which only four players from the top 10 have won on the PGA Tour, it might not be that easy. Congressional has been tough all week, and with another day of broiling sunshine, the fairways were running faster and the greens were turning slightly yellow.
Reed matched the highest score to par for a 54-hole leader in a tour event at Congressional. The other time was in 1983 at the old Kemper Open.
''That was one of those days that we were able to grind it out,'' Reed said. ''It played tough. It seemed to get firmer and faster as the day went on, and it was just a lot of adjusting you had to do during the round. We handled it pretty well, and luckily we have the lead going into tomorrow.''
Noh finished off his 5-under 66 - the best score of the third round - about the time the leaders went off. He was at 4-under 209, which looked better by the hour.
Jacobson made four birdies in his opening eight holes to reach 8 under, only to take double bogey on the 11th hole and a sloppy bogey on the par-5 16th hole. He wound up with a 71. Leishman was still only one shot behind until he failed to get up-and-down for par on the 17th and fell to a 73.
''At the start of the day, we probably knew that anything under par was going to be a really good score,'' Leishman said. ''I actually said to my caddie, `It feels a bit like a U.S. Open' because there were a few pins that you really didn't have a chance to get at. But I think that's good. It's a tough golf course. It's long. If you're not in the fairway, you have no chance.''
Reed was not in the fairway on two holes where he made birdie, and he managed to pulled it off.
In deep rough to the right of the fourth fairway, he was 169 yards away and decided to smash a 9-iron to clear the bunker instead of trying a soft 8-iron. It worked out perfectly. The ball bounded past the hole and up a slope, and slowly rolled back to within inches of the cup.
''I thought there was about a 3 percent chance I could cover that bunker, and I ended up being perfect,'' Reed said. ''It was nice whenever I saw it roll up the hill and I saw it come back down because I thought, `All right, we have about 5, 7 feet for birdie.' Didn't know it was a couple inches, which was nice.''
Oliver Goss of Australia, the U.S. Amateur runner-up last year making his second pro start, was part of a four-way tie for the lead going into the third round. He was still in the mix until a three-putt from 10 feet for double bogey on No. 11. He had a 76, though he was still only five shots behind.
Twenty players were separated by five shots going into the final round, and the name that stood out was former U.S. Open champion Justin Rose.
Rose was within two shots of the lead after a hot start, only to make bogey on the par-5 ninth and a double bogey on the 11th hole. He battled back with a pair of late birdies, only to drop another shot on the 18th for a 71. Even so, he was only three shots behind.
This could be a perfect fit for a U.S. Open champion. None of the last 26 players who teed off broke 70. Rose took note of the rapidly changing color of the greens, and his only fear was officials watering the greens overnight, which would make it easier for the early starters.
''I'd be a fan of them letting them go a little bit and making this a tough tournament and sort of having another U.S. Open,'' Rose said. ''That would be my wish right now. But obviously, the course is firm. Wedges were releasing 10 yards by the end of the day. It's definitely a test. It was fun. I enjoy that type of golf.''