Apocalypticism is a trend found within Judaism, Christianity, and Islam almost exclusively, and that can be described broadly as a theological emphasis on a climactic end of the world in which divine intervention--e.g. a divine judgment of all people, a divinely-led battle, a divine endorsement of a new world, etc.--plays a role. The Christian Right is particularly influenced by an apocalypticism common among conservative Evangelicals, Fundamentalists, Pentecostals, and most Protestants in the Charismatic movement, in which the End Times concludes with the Second Coming of Jesus Christ.
Apocalypticism is usually marked by distinctive apocalyptic rhetoric and, often, symbolism. Within the Christian Right, such rhetoric tends to focus on the role of the modern nation of Israel, notions of an Antichrist who will lead a worldwide movement against Christians, and increasingly belief in a divine role for the United States in End Times. Throughout Christian history in particular, apocalyptic rhetoric has been used by both progressives and conservatives, reformers and reactionaries, and has echoed radically different themes, including during the Middle Ages the idea that Natives Americans were the "lost tribe" of ancient Israel and the idea of the destruction of the Church and its priesthood as a divine calling for the poor; (see Norman Cohn's The Pursuit of the Millennium). In recent decades, progressive Christians use of apocalyptic rhetoric is less common, generally metaphorical, and focuses more often (though not always) on themes of unification, reconciliation, and harmony instead of destruction.
(see Frontline's "Apocalypse!")
Note. Through the influence of the Christian Right, belief in an apocalypse has affected American domestic and foreign policies on issues ranging from the environment to Israel. Many on the Christian Right believe it is biblically prophesied that key events will occur during the End Times in Israel. Apocalypticism among many conservative Protestants leads many of them (with those ascribing to Dominion Theologies being notable exceptions) to have a pessimistic or fatalistic view of the futures of humanity and the Earth.
Note. Apocalyptic thought almost always include:
1) a target (i.e. some place, race, class, nation, group, person, etc. is focused on; throughout Christian history apocalyptic thought most commonly targeted Jews as agents of evil)
2) the purgation of the target (i.e. the target is or will be cleansed, destroyed, or otherwise dramatically affected by fire, water, magic, divine power, human might, etc.);
3) historicity (i.e. the apocalypse happens at least in part within the context of human history--in real time and space, not in some heavenly realm or other place or reality that could not be observed by human beings).
One example of the above three elements is in the End Times apocalypticism of Protestant Christianity as mentioned above, in which a prerequisite for the Second Coming of Jesus is the destruction of the Antichrist and all non-Christians following the Battle of Armaggedon.
Historical note. The term apocalypticism itself dates from the 1850's, though it describes a general type of theological movement that has existed in numerous religions as far back as the 600's B.C. and Zoroastrianism (see Avesta.org).
(see entry for "apocalyptic" in Frontline's "Apocalypse!" glossary)