That would be 1988, and before that 1984, and before that 1980, and before that 1976, and before that 1972.
As you probably know there are 18 states (plus DC) that have voted Democratic in the last six presidential elections, and slightly more than half of them went for Bush in '88–that includes Maine, as noted.
1988 is a whole different world though compared to the electoral map that we’ve come to expect. Winning a vote in Maine would be highly significant.
I doubt that Maine, even the 2nd district, will go for Trump, Stein or no Stein. That being said, if the race is close a few votes *could *make a big difference, and it’s not out of the question that the race in Maine could be close. Maine is after all a heavily, heavily white state; it has had some economic issues that notably affect blue-collar workers (loggers, manufacturers); it doesn’t have an especially high number of college graduates for an ordinarily blue state. It has in short more “angry white men” than Maryland, Connecticut, Minnesota, Washington, or most other typically Democratic-leaning states.
I don’t *really *think Maine will be all that close. And I don’t think Stein, when all is said and done, is going to be attractive to enough Mainiacs to deny the state to Clinton. Still and all, if I had to choose a traditionally blue state that just *might *go to Trump this time around, Maine would be at or near the top of my list.