Mike Minogue crushed Brian Shortsleeve with 76% of the vote in the Massachusetts Republican gubernatorial primary, advancing to face Democratic Governor Maura Healey in November.
Healey, seeking a second term and unopposed in her primary, enters the general election with a 19-point lead over Minogue in an earlier 7NEWS/UNH poll.
Andy Smith of the University of New Hampshire Survey Center said Minogue must energize Republicans and win over unenrolled and independent voters to overcome the GOP's registration disadvantage.
Massachusetts remains heavily Democratic, but its governorship has often flipped parties over recent decades, with Republicans including Mitt Romney winning the office despite the state's deep-blue lean.