Consciousness of social and historical reality, falsified and constrained by class interest. It has therefore existed since the split of society into classes. Only the appearance of a universal, exploited and revolutionary class generates the conditions that make possible its theoretical demolition -in its political expressions- and its practical demolition, in its revolutionary practice.
Ideology and the ruling class
All ruling classes until now have needed, in order to maintain the system that gave them meaning, to present exploitation as an inevitable and "natural" fact. The sets of ideas and prejudices, "common sense", culture, art and common beliefs reflect this. Since the production of ideas is part of the productive apparatus of society itself, the ideological production of an era disseminates the interests and points of view of the ruling class as universal values, reproducing and consolidating the values with which it justifies its rule.
The ideas of the ruling class are in every epoch the ruling ideas, i.e. the class which is the ruling material force of society, is at the same time its ruling intellectual force. The class which has the means of material production at its disposal, has control at the same time over the means of mental production, so that thereby, generally speaking, the ideas of those who lack the means of mental production are subject to it.
The ruling ideas are nothing more than the ideal expression of the dominant material relationships, the dominant material relationships grasped as ideas; hence of the relationships which make the one class the ruling one, therefore, the ideas of its dominance.
The individuals composing the ruling class possess among other things consciousness, and therefore think. Insofar, therefore, as they rule as a class and determine the extent and compass of an epoch, it is self-evident that they do this in its whole range, hence among other things rule also as thinkers, as producers of ideas, and regulate the production and distribution of the ideas of their age: thus their ideas are the ruling ideas of the epoch.
Marx and Engels. The German Ideology, 1845
All ruling classes need to present their programs and needs as universal advances, as goals of society as a whole. And they need to do so, first of all, before themselves. We have no reason to think that the bourgeoisie is not sincere when it identifies the "interest of all" with the interest of the nation -that is, that of national capital- demanding that we willingly accept worse living and working conditions or that we massacre each other in a war.
But the bourgeoisie cannot conceive of any form of social organization other than its own, the one that gives it meaning as a class. If it could, it would be calling itself into question. The ideology of the ruling class is not just a mask: it limits its conception of society and the world insofar as it cannot conceive that its interests clash with those of society as a whole. Ideology is an interested and false consciousness of reality, limited and limiting.
Ideology under state capitalism
Under state capitalism it is not individuals from the upper bourgeoisie, directly and personally, as was relatively common in its centuries of ascent, who elaborate the ideological forms that "oil" the system and serve as its guide in exercising its rule. Ideology is not a Machiavellian product emerging from a state or corporate cabinet that thinks openly in terms of class struggle. It is a social product, produced organically within the specialized apparatuses of capital.
There are organs of the state, such as the university, political parties, the media, trade unions, think-tanks and all kinds of groupings, specifically dedicated to creating ideology by absorbing "trends", weighing up their consequences and promoting new "causes" and worldviews.
These professional ideologues generally belong to the petty bourgeoisie, and much of what they produce bears its stamp, from populism to feminism. Given the nature of this intermediate class and its reactionary expectations, nothing it can create is really a real danger to capitalism as such, although it may occasionally put a spoke in the wheel of the interests of national capital or its leading factions.
The "protest" ideologies of the petty bourgeoisie throw sand in the eyes of discontent and anger. Of course, this may well be unconscious on the part of those who put them forward, which is why it is ideology, but it takes on materiality as it is socially produced, that is, as it elicits the consensus of different sectors of power, building itself up as a "social truth" through the media and the action of the political apparatuses dedicated to regimenting the population under the state and the interests of national capital.