Wiktionary
n. (context US idiomatic politics English) A state which may vote Democratic or Republican, in a given election or generally; a purple state.
Wikipedia
In presidential politics of the United States, a swing state (also, battleground state or purple state, in reference to red states and blue states) is a state in which no single candidate or party has overwhelming support in securing that state's electoral college votes. Such states receive a large share of the attention and campaigning of political parties in presidential elections, since winning these states is the best opportunity for a party to gain electoral votes. Non-swing states are sometimes called safe states, because one candidate has strong enough support that they can safely assume that they will win the state's votes.
Swing State is feature-length documentary (released in 2008), written, produced and directed by John Intrater, Jason Zone Fisher, and H. Spencer Young. Full credits available at