"Capitalism must draw upon cultural ideas that exist outside circuits of profit-making, some of which support the norms and structures of capitalism and some of which are critical of capitalism...capitalism needs both types...critical voices are productive and fruitful for capitalism, forcing capitalism to evolve and temporarily resolve some of its contradictions thus preserving it as a system for the long haul. Indeed, capital's ability to periodically present a new set of legitimating principles that facilitate the willing participation of society accounts for its remarkable longevity despite periodic bouts of deep crisis." - Nicole Aschoff, 2015
"NOTHING is more surprising to those, who consider human Affairs with a Philosophical Eye; than to see the Easiness with which the many are governed by the few, and to observe the implicite Submission with which Men resign their own Sentiments and Passions to those of their Rulers. When we enquire by what Means this Wonder is brought about, we shall find, that as FORCE is always on the Side of the Governed, the Governors have nothing to support them but OPINION. 'Tis therefore, on Opinion only that Government is founded; and this Maxim extends to the most despotick and most military Governments, as well as to the most free and most popular." - David Hume, 1742
How has our understanding of ideology advanced in the last 275 years? By the eighteenth century (and arguably earlier), we already understood that the powerful can only maintain their power through ideology.
From that point it would seem to follow trivially that ideology which is successful will have to incorporate criticism and accommodate adjustments to changing circumstances. This is not unique to capitalism. If you are King John and your rule is under threat by a gang of rebel barons, you may have to abandon the legitimating principle of vis e voluntas for the principle of treaty embodied in the Magna Carta. This move is functionally identical to capitalism's ever-shifting reliance on arguments of efficiency, meritocracy, and so on.
There are of course unique particularities to our present situation. For instance, because power in capitalism is depersonalized, the vicissitudes of ideology emerge not from some clever monarch changing his justifications, but from a vast apparatus of academia, marketing, electioneering, and so on. This is certainly interesting with regard to ideological production, that is, the process which creates and promulgates expedient ideology. Where before we had some individual intelligence playing politics, now ideology seems to emerge from a self-organizing process wherein some messages get amplified and others remain lost in the din of public discourse.
But does this difference in ideological production - perhaps the most substantial insight we've gained into ideology since Hume - have any practical consequence for people who want to contest power?
Two possibilities seem likely to me. The first is that it doesn't, and that much of our political thought about ideology over the past three centuries has been a tactical spinning of wheels. Powerful people invent pretexts for staying in power, and our task is to debunk them through the hard work of critique and persuasion. It doesn't much matter that the ideology is coming from our marketers and politicians rather than from, say, royal proclamations; what matters is that we resist.
The second possibility is that the particularities of ideological production in capitalism do matter, though in a way we should find disquieting. Capitalism draws on the whole of the public imagination for its raw materal; it relies on a kind of marketplace of ideas to select among them; and it reacts in real time to ideological challenges, sometimes disseminating rebuttals even faster than the challenges themselves. It is something like what various biologists and computer scientists have referred to as a superintelligence: adaptive, spontaneously organizing, and aggregating the cognitive machinery of much smaller parts.
This latter understanding maps pretty closely onto conceptions of ideology advanced by writers like Ellul and Althusser, but I think the consequences are, in this formulation, much clearer. Critics of capitalism are not vying with some comparable intelligence like a king of a faction of aristocrats -- they are decisively and thoroughly overmatched by the collective wisdom of entire populations. In that case, there is no reason to assume that individuals can come up with criticism fast and effective enough to overcome capitalism's vast stores of creativity and capacity for adaptation.
Still, I suppose one must try.