It does seem like during the Cold War, there were significantly more states that could flip in one direction or another, so "swing states" weren't so important as a concept. The last time there was a single coherent set of swing states which decided elections that were important for a while was in the post-Civil War period, when you had roughly the same set of swing states deciding close elections from 1868-1916 (and literally the same set 1876-1888). Wonder if they had a different term for places that flipped a lot, like Indiana and New York.
The term "bellwether state" is similar in meaning and much older.
