If you watched any number of last year’s Democratic primary debates, there’s a good chance you noticed one of their most overt and recurring patterns: namely, a near total hostility toward the idea of a universal, single-payer health care system.

At times, this hostility could be almost baroque, with one voice or another invariably shouting it from the TV screen any time the subject of health care was broached. This extended not only to most of the candidates themselves (Bernie Sanders being the sole contender to unequivocally champion Medicare for All) but also to the panelists and commentators featured on the cable networks that hosted the debates. As Sanders himself pointed out during a Detroit event hosted by CNN, even the ad breaks generally offered no solace to those hoping for even a momentary cessation of the barrage: health insurance and pharmaceutical companies seizing every opportunity to bombard viewers with misleading industry agitprop about the breathtaking wonders of profit-driven health care.

On its face, the existence of this advertising effort likely surprised no one. Wherever their politics happen to sit, and whether they sympathize or not, most Americans probably grasp the idea of an industry using ad space to protect its business model. Even the hostility toward Medicare for All then expressed (and still expressed) by many Democratic politicians has a fairly straightforward explanation: a whopping majority of voters, after all, favor campaign finance reform and believe donations from corporations and special interests have a direct influence on the decisions those running for office make. It requires no great leap of the imagination to understand that politicians raising funds from figures in the very industry threatened by a particular policy aren’t going to be its most vocal champions.

This is what arguably makes the hostility directed toward Medicare for All by figures at the cable networks themselves the most insidious of all. Consider the following question, posed to Sanders during the Detroit debate by CNN’s Jake Tapper:

Let’s start the debate with the number-one issue for Democratic voters, health care. And Senator Sanders, let’s start with you. You support Medicare for All, which would eventually take private health insurance away for more than 150 million Americans in exchange for government-sponsored health care for everyone.

Despite his attempt at a somewhat balanced framing, and whether he realized it or not, Tapper was essentially regurgitating a talking point seeded by the insurance industry and its lobbyists (just take it from former Cigna-executive-turned-whistleblower Wendell Potter). Regardless, a question from a journalist tends to carry a lot more weight than a TV ad or even a spiel from a warm-and-fuzzy-sounding liberal politician.

We can’t know, obviously, how Tapper genuinely feels about the issue or even what role he played in writing the question. Given the near total uniformity of hostility to Medicare for All expressed on large cable networks, it’s far less relevant than the disjuncture between the perspectives they tend to showcase and majority public opinion — which consistently favors the creation of a universal, single-payer model.

The existence of media bubbles, of course, is one obvious explanation: exorbitantly well-paid and often politically insular communities of pundits and cable hosts inhabiting a completely different socioeconomic reality and being far better served by the current health care system than most Americans. To really understand why cable networks were so hostile toward Medicare for All throughout the Democratic primaries (and why they almost certainly will be for the foreseeable future), however, we have to ultimately look at their business model. Consider the following point made by Institute for New Economic Thinking executive director Rob Johnson during a recent interview when asked about Medicare for All:

Public opinion polls show more than 70 percent of the population is in favor of Medicare for All. It’s not the population that doesn’t want it, and they’re the ultimate voters. It’s vested interests and the struggle that has to do with the relationship between money-raising campaign war chests and the probability of re-election and what you might call the refractory influence of the mainstream media, where pharmaceutical companies in particular and insurance companies as well are very big advertisers. [emphasis added]

Concise though it is, Johnson’s remark is fairly close to a comprehensive explanation of why Medicare for All remains so marginal throughout the political class, despite the overwhelming popular support it boasts. What he calls the “refractory influence” of the mainstream media is arguably the most crucial factor involved: given the dependence of large networks on health insurance and pharma companies for advertising revenue, it’s really no wonder the astroturfed effort to discredit socialized medicine enjoys something approaching full-spectrum dominance on cable TV. As Noam Chomsky and Edward S. Herman wrote in their famous study Manufacturing Consent: “The power of advertisers over television programming stems from the simple fact that they buy and pay for programs — they are the ‘patrons’ who provide the media subsidy.”

CNN’s Detroit debate is a case in point; the network was demanding at least $300,000 from companies advertising, with a single thirty-second spot costing an estimated $110,000 — and groups like the so-called Partnership for America’s Health Care Future (in practice, a front for various corporate interests), filled out many of the slots. Regardless of how anchors or hosts think about an issue like health care, the networks’ basic model essentially precludes meaningful critique of the status quo by design. As long as it persists, don’t expect to see the public interest or popular opinion reflected anywhere on cable TV.