As rain-softened Augusta National surrendered unprecedented success, Thomas closed with back-to-back birdies to shoot a three-under 69 and US compatriot Johnson birdied his final hole to shoot 70 and join the lead pack on nine-under-par 135.
“I like my position going into the weekend,” Johnson said. “Conditions are going to stay relatively the same. You are going to have to stay aggressive. You have to keep shooting well.”
Smith closed with an eagle and three birdies to shoot 68 while Ancer, trying to become the first debut Masters winner in 41 years, birdied two of his last four holes to fire 67.
“It was a very up and down round, a little bit scrappy,” Smith said. “But hung in there and at the end, it was brilliant.”
Im Sung-jae, a 22-year-old South Korean also making his Masters debut, fired a 70 to share fifth with American Patrick Cantlay on 136.
“I really feel like I’m prepared this week,” Im said. “I did feel like this course suited my style. I just approached the tournament with confidence.”
Three Englishmen were another stroke adrift - reigning Olympic champion Justin Rose, 16th ranked Tommy Fleetwood and 2016 Masters champion Danny Willett.
“With it being softer this year, some flags are a hell of a lot easier,” Willett said. “Some are a lot trickier. But all in all you’ll see scoring better when the greens are softer.”
World number two Jon Rahm of Spain and Japan’s Hideki Matsuyama were both on 8-under, Rahm 5-under on the round with six holes to play and Matsuyama 4-under on the round with three holes remaining at sunset.
In all, 48 golfers must finish round two on Saturday morning.
With a Thursday rain delay forcing a Friday first-round finish, golfers stung Augusta National for the lowest opening-round scoring average in Masters history, 71.43 strokes, with 53 players under par in round one and 24 scores in the 60s, both Masters round records.
Germany’s 63-year-old Bernhard Langer became the oldest player to make the cut in Masters history on 141. An expected 1-under cut line would be the lowest in Masters history.
The low cut line could also spell trouble for Bryson DeChambeau.
The big-hitting American, who had been tipped to overpower the Augusta layout, is one over par with six holes of the second round left to play.
DeChambeau could be left ruing a triple-bogey seven on the par-3 third, which was followed by three more bogeys before the turn.
Four-time major winner Rory McIlroy, seeking a green jacket to complete a career Grand Slam, completed a 75 in the storm-hit first round yesterday, then rebounded with a bogey-free 66 to revive his chances.
Defending champion Tiger Woods, who matched his best-ever Masters start with a 68, was on level par for the second round after 10 holes, sharing 22nd place as he chases a 16th major title and sixth Masters victory.
Johnson reeled off three birdies in Amen Corner, Augusta’s famed 11th and 13th holes, then followed with back-to-back bogeys and pars all the way until his closing birdie.
“Played real solid, had a lot of good looks, none of them seemed to want to go in,” Johnson said. “But it was nice to finish with a birdie.”
Ancer has seen enough
World number 21 Ancer, who hadn’t seen Augusta National before playing 27 holes on November 4, hasn’t felt troubled on a course where experience is considered a vital asset.
“It has been fine,” Ancer said. “I’ve been able to get it up and down or make birdie from the pine straw. It has been a lot of fun. I feel good.”
Neither Ancer nor Smith has ever held a 36-hole lead on the US PGA Tour.
The Masters was postponed from its usual April date by the COVID-19 pandemic, which also forced the event behind closed doors as a safety move.
Yesterday morning, Johnson finished his opening-round 65, his lowest career Masters round and first without a bogey.
Thomas, the 2017 PGA Championship winner, finished a first-round 68, having never shot better than a 73 in four prior Masters opening rounds.