Historical Midterm Wave Elections: 1994, 2006, 2010, 2018 Patterns

Analyzing the four major wave elections reveals a consistent pattern. First, sustained presidential approval below 45% for at least 6-9 months before the election. In every wave, the president's party suffered catastrophic losses; in every non-wave midterm, presidential approval was either above 50% (1998 Clinton, 2002 Bush post-9/11, 2002 midterm being the lone exception to the out-party-wins rule) or the wave was blunted by a powerful countervailing issue. Second, a high-salience mobilizing issue that energizes the out-party base: Iraq War dissatisfaction drove 2006's Democratic wave; Obamacare opposition drove 2010's Tea Party wave; Trump's style and healthcare threatened in 2018 drove the Democratic wave. The issue must reach voters who are not already reliably activated partisans.

The 2022 non-wave is instructive. All structural indicators pointed to a large Republican wave: Biden approval was 43%, inflation was at 40-year highs, the generic ballot favored Republicans. But the Dobbs Supreme Court decision in June 2022, eliminating the federal constitutional right to abortion, dramatically increased Democratic enthusiasm and motivated low-propensity Democratic voters — particularly suburban voters — to turn out. The result was Republicans gained only 9 seats, well short of historical expectations. The 2022 result demonstrated that a single high-salience mobilizing issue for the out-party can compress or eliminate an expected wave.