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.
[5][6] Political analyst Charlie Cook describes wave elections as the result of an "overarching, nationwide dynamic," such as a high or low presidential approval rating, economic conditions, and scandals.
[7][8] Cook contrasts wave elections with "micro-elections" in which neither party makes significant gains, and candidates, local issues, and other factors not strictly related to party alignment have a stronger role than in wave elections.
[8] A pick-up of 20 seats in the United States House of Representatives has been used as a cut-off point by analysts such as Stuart Rothenberg.
[12] Congressional incumbents in the United States enjoy an electoral advantage over challengers, but a wave election often boosts challengers, resulting in many more incumbents losing than usual during wave elections.