Isner sweeps Harrison in Newport
The 6-foot-9 Isner rode his big serve to win his 11th straight match on Newport's grass courts.
He was not broken in the match that lasted 1 hour, 20 minutes, taking control by blanking Harrison in the tiebreaker.
Isner, seeded second, broke in the third and seventh games of the second set before Harrison hit a backhand return long on the match's final point.
The 28-year old Isner showed no effects from a left knee injury that forced him to retire from his second-round match at Wimbledon.