The terms “battleground state” and “swing state” refer to states that have closely divided support for Democratic and Republican presidential candidates. They are also sometimes called “purple states.”
Presidential campaigns are waged mainly in these battleground states as the outcomes in most other states on the electoral map are mostly known well ahead of the election.
Using Google’s Ngram Viewer, there was an uptick in the term’s use in 1980 before a significant jump in the very tight 2000 presidential election. Swing state was a more popular term for closely contested states in presidential politics beginning in the 1960s.
By 2004, “battleground state” overtook swing state in popularity but both phrases are still used by most journalists.
University of Minnesota Professor Eric Ostermeier analyzed the frequency of use for both phrases during the 2012 presidential election and found a spectrum of usage from ABC News’ 2.5-to-1 ratio of battleground state to swing state to MSNBC’s 1.8-to-1 ratio of swing state to battleground state.
In contrast, the similar phrase “toss up state” was used only 29 times in the six months of reviewed reports.
A related term in politics is bellwether.