ABSTRACT
This chapter describes the political parties are powerfully shaped not only by the people who lead and participate in them but also by the environment in which they act. The nature and concerns of the voting population are vital influences on a party system. The societal "fault lines" that divide voters into opposing groups—race is one of the clearest and most persistent examples in American politics—help to define the parties' issue agendas. Most democratic nations do not divide governmental powers so insistently among different branches and levels of government. The strength of the party in government means that the party organization's leaders have few effective tools to keep party legislators and other elected officials acting in accord with the party's stands. Voters' loyalty to the parties weakened during the late 1960s and 1970s, a time of upheaval in many aspects of American life. The American parties have never lacked interesting challenges.
