"As Maine goes, so goes the nation" is a phrase that at one time was in wide currency in United States politics. The phrase described Maine's reputation as a bellwether state for presidential elections. Specifically, Maine's September election of a governor predicted the party outcome of the November presidential election in 19 out of the 26 presidential election years from 1832 to 1932, or 73 percent of the time. The accurate years were from 1832 (if not earlier) through 1844, in 1852, from 1860 through 1876, in 1888, from 1896 through 1908 and from 1920 through 1932.
Beginning with its creation as a state in 1820 when it split off from Massachusetts, Maine held its elections for statewide and congressional offices in September, not November as did most other states, due to warmer September weather and Maine's early harvest.   (Maine did hold its presidential elections in November.) 
Maine's reputation as a bellwether began in 1840, when it voted in Edward Kent, the Whig Party candidate, as Governor of Maine. Two months later, the Whig party Presidential candidate, William Henry Harrison, won the 1840 presidential election.  Again in 1888 Maine voted solidly for Republican Party candidates, and Republican Benjamin Harrison won the Presidential election despite losing the overall popular vote nationwide.  The saying originated following this election, though it is unknown by whom.  In subsequent election cycles, national political parties often went to considerable lengths to win Maine's early Congressional and statewide elections, despite the state's relatively small population (and hence few seats in the House of Representatives, and few electoral votes in the November presidential elections) and somewhat remote location.
In 1936, Maine elected a Republican Governor, Lewis O. Barrows, an overwhelmingly Republican state legislature, and an all-Republican congressional delegation in its early balloting, and Republicans trumpeted the phrase. Maine had elected a Democratic Governor and two Democratic congressmen in both 1932 (although the state had still been carried by Republican President Herbert Hoover that November) and 1934, and the Democrats had been making gains in the Maine Legislature, so the Republican victories in Maine in September 1936 may have seemed indicative of a national Republican trend. That November, however, only Maine and Vermont were carried by Republican nominee Alf Landon over President Franklin Delano Roosevelt in the 1936 Presidential election, giving Landon only eight electoral votes (the three from Vermont and the five from Maine),  equalling the smallest total ever (as of 2016 [update]) won by a major-party nominee since the beginning of the current U.S. two-party system in the 1850s, and destroying the credibility of the phrase permanently. (Landon had such a bad election that he did not even win his home state, Kansas.) Democratic strategist and F.D.R. campaign manager James Farley quipped "As Maine goes, so goes Vermont."   From then on, the party whose nominee won Maine's September gubernatorial election in presidential election years went on to win the November Presidential election only once—in 1952, when Republican Burton M. Cross was elected Governor and Dwight D. Eisenhower was elected to his first term as President.
In 1957, Maine changed its election law to hold all general elections in November. Beginning in 1960 it held elections at the same time as the rest of the United States,  ending the tradition of early voting.
- Harkavy, Jerry (1998-09-06). "'As Maine goes' tradition went - long ago". AP/South Coast Today.
- "2006 Campaign Tip Sheet - Maine state profile". National Journal. Archived from the original on 15 November 2006. Retrieved 2006-10-13.
- Mills, Paul H. (2006-09-10). "'As Maine goes'". Sun Journal (Lewiston, ME).
- Speel, Robert W. (1994). "Chapter 2: Vermont, the North, and Realignment". Changing Patterns of Voting. Penn State Press.
- Morison, Samuel Eliot (1972). "Chapter XII, The New Deal". The Oxford History of the American People, Vol. 3. p. 328.
- Ken Rudin (2000-07-14). "The Significance of the V.P. Pick". The Washington Post.
- "As the Nation Goes". Time Magazine. September 23, 1957.
- New Mexico became a state in 1912. In presidential elections from 1912 to 1972, both years inclusive, it cast its electoral votes for the winning candidate. See http://www.270towin.com/states/New_Mexico