From the founding of the
Republican Party in the 1850s until the 1960s, only Republicans won general elections for Vermont's statewide offices. One method that made this possible was the Republican Party's imposition of the "Mountain Rule," an informal mechanism which restricted the pool of candidates. Under the original provisions of the Mountain Rule, one U.S. senator was a resident of the east side of the
Green Mountains and one resided on the west side. The expanded version of the rule called for the governorship and lieutenant governorship to alternate between residents of the east and west side. Nominees for governor and lieutenant governor were originally allowed two one-year terms, and later one two-year term. For nearly 100 years, likely
Republican candidates for office in
Vermont agreed to abide by the expanded Mountain Rule in the interests of party unity. Several factors led to the eventual weakening of the Mountain Rule, including the long political dispute between the
Proctor (conservative) and
Aiken–
Gibson (progressive) wings of the party; primaries rather than conventions to select nominees; the direct election of
U.S. Senators; and several active third parties, including the
Progressives, the
Prohibition Party, and the
Local Option movement. In the 1960s, the rise of the
Vermont Democratic Party and the construction of
Interstate 89 also contributed to the end of the Mountain Rule. Although I-89 is a north–south route, it traverses Vermont from southeast to northwest for the majority of its length within the state and changed the way residents view how it is divided. ==List of governors==