The 22-year-old Texan has now held the outright lead for a record seven consecutive rounds and if he can remain there one more day will join Tiger Woods, Nick Faldo and Jack Nicklaus as the only men to claim back-to-back Masters wins.
Spieth stays top a Masters despite late stumble
American rookie Smylie Kaufman, who still lives with his parents, had the lowest round of the day, returning a three-under 69 to join Spieth in Sunday's final pairing.
Spieth, who began Saturday's third round clinging to a one-shot lead, ended it in the same position after a wild afternoon at a windswept Augusta National, carding a one-over 73 that featured two double-bogeys on the back nine.
An 80th Masters that had looked ready to turn into a coronation will instead be up for grabs with an eclectic mix of challengers, including a Masters debutant, a 58-year-old former champion and a 24-year-old Japanese sensation all lurking.
American rookie Smylie Kaufman, who still lives with his parents, had the lowest round of the day, returning a three-under 69 to join Spieth in Sunday's final pairing.
Sitting two off the pace are evergreen German Bernhard Langer, a two-time Masters winner who showed he still knows his way around a tricky Augusta layout, carding a two-under 70, and Hideki Matsuyama, playing in his fifth Masters, who had 72.
World number one Jason Day of Australia also moved into contention with a 71 and will start the final round just three strokes off the pace.
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