Yes, Maine allots its electoral votes proportionately.
To my knowledge, it’s never happened, though. Maine has only 2 congressional districts.....with a population of nearly 1.3 million, we should have three, but we don’t.
In 2004, Kerry won both congressional districts; in 2000, Gore won both; in 1996 and 1992, Clinton won both. (I think Perot got more votes in Maine in 1992 than George H. Bush). In 1988, George H. Bush won both districts, and in 1984 and 1980, Ronald Reagan won both congressional districts.
The only other state that allots its electoral votes in a proportional manner is Nebraska.
Not quite. The winner of each electoral district gets one vote; the winner of the state as a whole gets two more. The EV's are not proportional. If the districts are 51%/49% and 51%/49%, the candidate who got 51% of the vote will get all four Electoral votes. If the districts are 49%/51% and 100%/0%, the winning candidate will only get three of the four EV's despite having 74% of the vote.
I'm not sure whether there would be any theoretical possibility of a 2-2 EV split; the only ways I can think of that that would occur would be (1) some or all parts of the vote resulting in ties, depending upon the tie-breaker rules in effect, or (2) oddities with certification and recounts (so that a candidate is certified as winning a district before a recount, which is conducted for the state as a whole, indicates he did not).