Entryism

Entryism (also called entrism, enterism, infiltration, a French Turn, boring from within, or boring-from-within) is a political strategy in which an organization or state encourages its members or supporters to join another, usually larger, organization in an attempt to expand influence and expand their ideas and program. If the organization being "entered" is hostile to entryism, the entryists may engage in a degree of subterfuge and subversion to hide the fact that they are an organization in their own right.