In times gone by, the State of Maine was always the tipoff state as to which party would be successful in electing the President. The saying was "As Maine goes, so goes the Nation" This was drastically changed in the 1936 Presidential election between FDR, running for his 2nd term, and Republican Alf Landon of Kansas. It was a landslide for the Democrats, with 46 out of the 48 states voting for Roosevelt, the only abstainers being Maine and Vermont. The saying was then changed to "As Maine goes, so goes Vermont"! Hal
Since 1988, Maine has just voted for whichever Democrat is on the ballot. Although Maine's electoral votes have been split by congressional district since 1972, 2016 is the only election in which the two have split their vote, with Trump getting 1 electoral vote from Maine's 2nd District, while its three CD-1 votes went to Clinton. With the demise of Maine's forest industry (and thus, it's unions), CD-2 has become more conservative, but CD-1 is where most of the people are.