Wave elections in the United States

Wave elections in the United States are elections in which a political party makes major gains. Based on the "red states and blue states" color coding convention in use since 2000, wave elections have often been described as either "blue waves" or "red waves" depending on which party makes significant gains, referring to a major increase in seats held by either the Democratic Party (associated with blue) in the former, or the Republican Party (associated with red) in the latter.

Source: Wikipedia — Wave elections in the United States (CC BY-SA 4.0)