Rumford, the runner-up at the Ballantine's last year, was bogey-free in the second round and is at 10-under 134 halfway through the tournament. Soren Kjeldsen shot 6-under 66 and is tied at 7-under for second place with Miguel Angel Jimenez, who had a second-round 67.
First-round leader Damien McGrane turned in an even-par 72 Friday and is in group of four players tied for fourth at 6-under.
Rumford had opened the first round with bogeys in two of his first four holes. Playing the back nine first, he started relatively slowly with a pair of pars but got under for the day with birdies at Nos. 12 and 14. He made the turn at 4-under after birdies at 17 and 18.
Rumford made a big move with four birdies in the five-hole span of 2-6 and pushed further ahead with an eighth-hole birdie.