Factionalism is a dimension of informal politics that is hardly unique to China, but it has become well entrenched there for several reasons. We know from available survey data that Chinese political culture is relatively low in trust, and the faction provides a particularly useful refuge from the tiger world of politics, organized as it is around that culturally sanctioned dimension of trust known as guanxi (connections) (Shi 2001 and 1997; Pye 1981). From an individual perspective, although this has been changing more swiftly in society at large via marketization, the institutional landscape of elite politics is still dominated by the looming presence of a single monolithic party-state, to which all auxiliary organizations are subordinated in a corporatist hierarchy; any smaller and more personally useful organizations must be formed sub rosa on a self-help basis. From a structural-functional perspective, the faction serves several functions neglected by party-state corporatism: it services individual careers, in both a defensive and an offensive capacity (i.e., to protect against damaging criticism or purge, and to mobilize support for upward mobility); it provides a way of mobilizing minimal coalitions in policy conflicts; and it may even provide a microcosmic unit beyond the family for social identity and solidarity. Factions have always been rampant in Chinese Communist Party (CCP) politics, but precisely because of the universally acknowledged propensity for factionalism, they are formally proscribed by the Leninist rules of innerparty life and hence exist only semiclandestinely, looming more clearly when the central leadership weakens or is in dispute (as, for example, during a succession crisis). Factions are assembled on the basis of a combination of one's formal and informal “bases” (zhengzhi jichu), the formal consisting of trusted colleagues and subordinates in one's current work unit, the informal consisting of ties made during one's previous socialization or career and carefully cultivated thereafter. Factional activities may most easily be understood according to realist or realpolitik methodological assumptions, but as we shall see, they need not operate in an ideological vacuum. Inasmuch as factions exist tacitly and become politically operational opportunistically, the precise affiliation of a given political actor may change over time depending on the issue at stake and other circumstances; hence faction membership can never be tabulated with certainty, even by faction leaders. A given political actor may have at his or her disposal a range of connections that varies in chronological depth (i.e., spanning x generations) and institutional breadth (i.e., spanning x organizational hierarchies). At a given time and place, the actor may need these categories to define him- or herself factionally. On such occasions, a strong factional network (i.e., one that has been assiduously cultivated over time) is useful and perhaps even indispensable to the actor's survival and highly useful for the pursuit of future political ambitions.