The first basic power technique addressed in this handbook was force; the second was economic control. The third basic technique is mental control or ideology. These are general categories and we can fit most, if not all, of the rest of the power techniques that we'll discuss under them: elites control people by coercing them with force, compelling them with economic incentives, and/or conning them to conform.
There are many specific techniques that fall under each of these broad categories, but ideology is perhaps the most varied is its control devices, especially in our post-modern, media-saturated world.
Unlike the compulsion of force or incentive, ideology is aimed at getting people to willingly control themselves. We're not talking about mental control through hypnosis, subliminal messaging, computer-brain interfaces, or other fictions that are the stuff of conspiracy theories. We're talking about the basic fact that ideas, along with semi-conscious and subconscious psychological factors, guide and control human behavior, and all of these are subject to external influence. Ideology, then, means elites guiding the behavior of large numbers of human beings by controlling, or at least having hegemony over, the ideas and beliefs that they use as guides for how to act. Not mind control, but simply myth, propaganda, and advertising; these create in the demos what Marx called "false consciousness," or a set of beliefs that support a society that ruins and despoils the lives of common people, but which they willing endorse anyway.
All societies tell stories; groups of people create and spread narratives that help them understand and orient themselves to their natural and social world. The stories that a society tells itself direct it's members to act in some ways, but also close off some possible courses of action by preventing them from being thought in the first place. These narratives take different forms: some make up a group's background lifeworld of shared understandings, some are discourses about more immediate concerns, large and small; some are descriptive, some are normative. All help to make a society what it is.
Whereas earlier, less technological societies mainly relied on religion, ancestor worship, tribal norms, or at most the virtue ethics of the res publica to establish controlling ideas, during modernity the media channels and institutions for spreading ideas have proliferated and so created a multiplicity of techniques and institutions of ideological control: from books and newspapers, to film and television, to the internet and social media; from schools and churches, to universities and think tanks, to foundations and advertising firms. The very proliferation of means of communication may help explain why the world in the early years of the 21st century seems stuck and unable to make progress, for currently there are a great many methods for ideological stabilization of society in its current state.
Ideology works to undermine democracy in multiple ways. Ideas influence behavior, so getting people to buy into the system makes them controllable and exploitable. This can be done by convincing common people that the current system is advantageous to them, even when it is not; or you can convince them that it is natural and unchangeable, so that they think there is no alternative. Either way reduces impulses and forces of resistance and therefore forestalls systemic social change and revolution. While I would try to offer an inclusive list here, ideology can work its pernicious effects in many other ways: it can be used to help divide and conquer the working class; to get people to submit to their own labor for exploitation; to promote consumerism that both distracts the people and profits elites. It can also shape basic perception as well as the formation of identity.