Large political parties are coalitions, not unitary blocks. Defections and reorganizations can be viewed as based on the behavior of the constituent factions within major parties. Such smaller factions can either switch allegiance between larger aggregates or, alternatively, split off on their own to form third parties. Political realignments and third-party movements, “by definition,” signal discontent with the prevailing parties. Third parties, gelling around neglected ideological issues, “indicate the failure of the system to integrate the emergent political demands of significant portions of the electorate” (Holt, Political parties and American political development from the age of Jackson to the Age of Lincoln, 1992). When sufficiently powerful, third parties force prevailing parties to absorb their pressures by incorporating, in part or full, the third party’s ideological grievance. Third parties are of interest in that the issues around which they coalesce are so often some mainstay of the liberal or conservative temperament, which has become neglected or unrepresented within the two-party system. Third-party movements arise when both prevailing political parties neglect a mainstay of each respective side’s temperamentally informed agenda. Elites often co-opt parties and use them for self-serving ends, causing political parties to become misaligned with political temperaments. Third-party movements are then seen as a corrective, bringing the party and temperament in line. Yet, as the examples within this chapter implicitly suggest, significant realignment and national third-party movements are powered as much by group competition as by ideological difference.