Which statement best defines electoral realignment?

Electoral realignment refers to significant, long-term shifts in the political landscape that alter the existing party system. The statement that identifies a change occurring approximately every 30 years accurately encapsulates the essence of electoral realignment by acknowledging that these shifts do not occur frequently but mark substantial changes in the way voters align politically over extended periods.

Realignments are typically characterized by a dramatic change in the patterns of party support, often influenced by major societal shifts, economic changes, or pivotal events. Historically, examples include the New Deal Coalition in the 1930s, which transformed the Democratic Party's support base significantly. These transformations can signify enduring changes in voter loyalty and party dominance, distinguishing them from transient shifts in voting patterns that may happen over shorter timescales.

While a shift in voting patterns over a decade could capture changes in voter preferences, it does not necessarily denote a fundamental change in the party system itself, which is crucial in understanding electoral realignment. The emergence of a new political party may occur but does not always signal an alignment unless it affects voter loyalties dramatically and enduringly. Stability in political party preferences contradicts the concept of realignment, which focuses on disruption and transformation rather than stability.