Steve Ford, Kevin Johnson, Chris Zambri, Zach Johnson, Mike Brisky and David McKenzie are tied for third place after shooting rounds of 3-under-par 68.
Branshaw began his round on the back nine of the East Course at the Country Club of Hershey. He posted two straight birdies from the 11th for a fast start and quickly moved to 3-under with a birdie on No. 14.
He settled down by rolling off six pars in a row. He climbed to minus-4 with a birdie at the par-4 third.
Branshaw put distance between himself and the field when he posted three consecutive birdies from the sixth to tie the course-record of 64.
Warren was steady throughout his round. He birdied the first before carding nine straight pars. He moved to 2-under with a birdie at the 11th.
Warren, who won the 2002 BMW Charity Pro-Am at the Cliffs, posted back-to-back birdies from the par-5 14th to grab second place.
Russ Cochran and Doug LaBelle II are among 12 players tied at 2-under-par 69.