According to the Library & Archives of New Hampshire's Political Tradition

"No incumbent president running for re-election and who had no significant opposition on the party's New Hampshire primary ballot has ever been defeated for a second term as president: Dwight D. Eisenhower in 1956, Lyndon Baines Johnson in 1964, Richard M. Nixon in 1972, Ronald Reagan in 1984, Bill Clinton in 1996."....George W. Bush in 2004?