Rahm's 7-under round was the lowest of the field on the South Course at Torrey Pines. He birdied No. 1 then holed out for eagle from 110 yards on No. 2 to set the tone for the day. He carded his first five of the round on the par-5 18th.
The 25-year-old is looking to claim his second Farmers Insurance Open win and fourth PGA Tour title.
Palmer, who relinquished the 36-hole lead he held after shooting 62 on Friday, will chase Rahm in Sunday's final group alongside Rory McIlroy. McIlroy holds a share of the third spot, three back of Rahm. The Northern Irishman posted 67 in Round 3 thanks to a flawless 3-under back nine.
Here's how the top of the leaderboard stands after Round 3:
|Place||Player||To Par||R3 Score|