swing statenoun [ C ]
uk/ˈswɪŋ ˌsteɪt//ˈswɪŋ ˌsteɪt/(in the United States) a state where the number of Democratic and Republican voters is about the same, that has an important influence on the result of the election of the United States President :
The outcome of the US election will be decided by a small number of swing states that are not decisively Democratic or Republican in their support for the presidential candidates.
This election sees familiar swing states such as Ohio, Florida, and Virginia in contention, as well as some new ones such as Utah, Arizona, and Wisconsin.