Mildred A. Schwartz
Party movements are organizations that have attributes of both political parties and social movements. Like parties, they desire a voice in the decisions of legislative bodies. Like social movements, they challenge existing power and advocate change, often using non-institutionalized means for expressing their message. They appear in the space left open by the failure of existing political parties and social movements to adequately represent their interests and achieve their goals. They may become independent parties or work within existing parties. Party movements can be found in most political systems. Their impact is felt whenever they are able to introduce new issues onto the political agenda, force traditional political parties to take account of their grievances, or change the contours of the party system.