The 21-year-old bounced back from his opening 74 with a nine-under-par round to sit six under at the halfway point in Hilton Head, South Carolina.
That left him just two shots off the lead held by fellow American Matt Kuchar, with Graeme McDowell one shot off the pace.
Kuchar followed his first-round 68 with a 66 and McDowell carded a 69 to go with his 66 from day one.
Spieth carded nine birdies in a flawless round to revive memories of his Masters heroics, when he led after every round to win by four shots.
American Peter Uihlein vowed to maintain his uncomplicated approach in pursuit of a second European Tour title after taking the halfway lead in the Shenzhen International yesterday.
Uihlein added a second round of 68 to his opening 67 at Genzon Golf Club to finish nine under par, one shot ahead of Thailand’s Kiradech Aphibarnrat, while two-time Masters champion Bubba Watson struggled to a 74 to lie nine shots off the pace on level par.
Aphibarnrat was two shots ahead of Argentina’s Emiliano Grillo, who birdied six of his last 10 holes for a 67, France’s Gregory Havret, England’s Matt Ford and South African Darren Fichardt.
Ford had been eight under par until bogeys on the 14th and 16th, while Fichardt also suffered from a poor finish following a hat-trick of bogeys from the 14th.
Italy’s Edoardo Molinari had earlier been disqualified for signing for an incorrect score in his opening 75, the former Ryder Cup player failing to include an unusual penalty incurred by his caddie.
Molinari wrote on Twitter: “Got DQ because my caddy jumped on a buggy between the 9th and the 10th hole yesterday. I didn’t see him unfortunately as I was 20 yds ahead. It would have been a two stroke penalty had I found out yesterday, DQ because I signed for the wrong card (which didn’t include the penalty).”
Korea’s An Byeong-hun could also count himself unfortunate after being forced to withdrew due to a neck injury. An was just one shot off the lead after an opening 67 which included a hole-in-one on the eighth, but was five over par for his second round before calling it a day after 14 holes.