Bradley came from seven shots back and stormed to the top with eight birdies to stand on 12-under 201 during the third round in ideal conditions at Ridgewood Country Club.
Bradley commenced his round holing a 10-footer for birdie and ended by sinking an eight-footer, with the pick of the rest finding the bottom of the cup with a 15-footer at the par-5 13th.
It was the 32-yar-old American's lowest score since an opening day 60 on the way to a runner-up finish in the 2013 Byron Nelson Classic.
"It was a decent round and I've been saying I can't remember the last time I felt that calm and together the whole round, from the very first tee," Bradley said.
"I actually felt calmer as the day went on. It's not really normally the case with me. That was fun."
Bradley, who has not tasted success since a third tour victory at the 2012 WGC Bridgestone Invitational, birdied his opening three holes and then five of his closing seven holes – in the process hitting all 18 greens in regulation and needing just 27 putts.
The Vermont-born but now Florida-based Bradley burst onto the world stage in stunning manner seven years ago by defeating compatriot Jason Duffner in his first major at Atlanta Country Club.
The triumph earned Bradley a five-year exemption into all four Majors but that expired at the end of 2016. He has competed in only five of the last eight since, having failed to qualify for the past two Masters and last year's Open Championship.
Bradley is currently 49th on the US PGA playoff standings with a top-30 showing to reach the season-ending Tour Championship ensuring his return to competing in all four 2019 majors.
The world number 67 said what he needs to reach that goal is more rounds like Saturday.
"It's going to take days like tomorrow, getting back in it, and days like today where I finish off a round like that," he said. "Days like tomorrow where I can go out there, whether I win, lose, shoot a hundred or whatever, I'm in it and I can feel that again.
"Any day like that is going to help me in the future."
Bradley posted his score three groups after Jordan Spieth walked from the course with a 64, matching his low round of the year from the last day of the Masters, to stand on 204.
Like Bradley, Spieth had a good day with the putter, managing just 25 putts and revealing he found something on the practice putting green ahead of his round.
After parring the sixth hole, Spieth was observed penning something into a notebook.
"I wrote down how I had set-up for the par on six so I wouldn't forget," he said. "I'll take a picture and put it in the notes. Just that trigger that gets me confident as I'm over the ball and not feeling like I have to manipulate anything."
Asked what he had written down Speith said: "Oh, that's something I'll keep, it's a secret of the pros and besides I think I've given you guys a lot already."