NORTON — The leaderboard took a seismic shake Saturday at the Dell Technologies Championship, triggered by the combined strength and swagger of first-year phenom Jon Rahm.

TPC Boston “does fit my eye,’’ said the free-swinging Spaniard, who carded a 5-under 66 and took sole possession of first place through 36 holes here at the bucolic 7,342-yard track originally designed by Arnold Palmer. “I mean, I think it’s a great golf course.’’

Paced by a blistering back nine that included five birdies, the 22-year-old Rahm high-stepped to the top of the board, while first-round leader Dustin Johnson, the PGA’s top money-earner in 2017, fell stagnant and failed to build on his opening-day 5-under par.

Johnson shot 1-over par for the day and wound up T15 at 4-under.

Rahm, ranked No. 5 in the world, will report to work Sunday with a two-stroke lead over the likes of Adam Hadwin, Paul Casey, Kevin Streelman, and Kyle Stanley, the latter of whom, along with Rahm, was the only early leader to stay in the thick of the chase after a strong start on Friday.

Otherwise, the top-end likes of Johnson, Sergio Garcia, and Marc Leishman all gave up considerable ground with their flat performances in Round 2. While Rahm, Hadwin, and Casey staked their claims at the top, the trio of Grayson Murray, Phil Mickelson, and Bryson DeChambeau all carded strong performances and settled three stokes back at 6-under par, along with Leishman.

“If I really thought about it,’’ said Hadwin, 6 under for the day and the lone Canadian among the leaders, “I could probably pick, like, 15 putts in these last two days I’ve been really happy with. Today, I made a bunch of putts early . . . so there’s probably too many to pick just one.’’

Superstar Jordan Spieth, who called Friday a “tough day at the office,’’ rebounded with a stellar 6 under in Round 2 to pull within four strokes of Rahm.

“A lot better than [Friday], for sure,’’ said a relieved Spieth, noting he inexplicably woke up on “the wrong side of the bed’’ to start the tourney. “I guess we all have days like that.’’

With Rahm’s day already wrapped up, Johnson started out with a pair of birdies on holes 1-2, trailing the ex-Arizona State star by only a pair of strokes. With 16 holes to go, and his confidence high, Johnson appeared poised to at least hold on to prime position for a championship charge these next two days.

But the 6-foot-4-inch Johnson soon wrapped a pair of bogeys around another birdie on the front nine, carried his 35 to the back, only to card double bogeys on Nos. 10 and 15. Riding high on Friday, shot down on Saturday. He made the cut with ease, but he’ll need to climb over a pack of 16 when play resumes at 11 a.m. on Sunday.

“I just figured [Johnson] was in the lead after the first two holes,’’ said Spieth, who played in the same trio with Johnson. “I thought we were just kind of gunning down DJ. But, yeah, [Rahm] posted two really solid rounds.’’

Golf being the soul crusher that it is, some of the game’s bigger names, including past TPC Boston champs, failed to make the cut at plus 3.

Rory McIlroy and Adam Scott both failed to earn a ticket to Round 3. McIlroy, 4 over, won it last year. He and Vijay Singh are the only men to win here twice. Scott, also 4 over, won the course’s inaugural event in 2003.

Rahm, who grew up the Basque region of Spain, has hit the pro tour with the same fury that he showed in college, where he became the NCAA’s only player ever to win two Ben Hogan awards as college’s No. 1 player. In June 2016, he was ranked No. 551 in the world, only to crack the Top 10 nearly a year later.

“It’s unbelievable what he’s done this year,’’ said an admiring Murray, who drilled a hole in one on No. 8 Saturday.

Already with $5.126 million in earnings this season, Rahm can pick up another $1.575 million if he can remain on top here through Monday. Ranked No. 129 at the end of last year, he is all but assured a berth among the 30 best who will play for the FedExCup $10 million bonus later this month in Atlanta.

“I feel I am on a good track,’’ said the Basque Basher, noting his game hit a lull midway through the season, when his motivation curiously dipped after he skyrocketed into the Top 10 rankings.

“It’s taken me two months to realize what I’ve done. Hopefully, I can keep surprising myself.’’

Kevin Paul Dupont can be reached at kevin.dupont@globe.com. Follow him on Twitter @GlobeKPD.