Millions of Americans have watched an astonishing mash-up video of dozens of local TV news reporters parroting word-for-word the political talking points dictated by their corporate overlords at Sinclair Broadcasting, the largest owner of TV stations in the United States.

Nearly 50 anchors warned of the threat “to our democracy” from (unnamed) journalists who use “biased and false news” to try “to control exactly what people think.” The video quickly went viral — and brought overdue attention to the little-known Sinclair broadcasting chain, which has been growing like a metastasized tumor, thanks to federal regulators who have set aside rules limiting commercial ownership of TV stations.

To be sure, other corporations have also pushed to deregulate broadcasting in an effort to corner market share and maximize profits. But Sinclair stands alone in its brazen use of the public airwaves to promote an extreme right-wing agenda to advance its business interests. From its hiring practices to its frequent disregard of journalistic values, the company is an unapologetic outlier among TV station owners.

At one time, journalists applying for jobs at Sinclair were questioned by the company’s owners about their views on abortion and other hot-button political issues — and turned down if they were “too liberal.” Sinclair’s news website found a way to get around this time-consuming process by hiring as reporters the Republican National Committee’s deputy press secretary and an operative for a right-wing provocateur. Sinclair executives also solicited donations from its news directors for the company’s political action committee, which finances candidates that support its conservative deregulatory agenda.

All of this is a dramatic departure from traditional newsroom norms, which try to maintain at least the appearance of neutrality. Indeed, most broadcast outlets discourage or prohibit political donations from journalists involved in campaign coverage to avoid any suggestion of bias.

But Sinclair seems less concerned about hewing to such standards. During the administration of President George W. Bush, the company censored an ABC News “Nightline” broadcast about American casualties in Iraq on the spurious grounds that it was “motivated by a political agenda designed to undermine the efforts of the United States.” Yet a few months later, Sinclair also aired portions of a discredited election-eve film attacking Democratic presidential nominee John F. Kerry as a traitor — and fired its Washington bureau chief for publicly dissenting from the company’s decision.

During the 2016 presidential campaign, Sinclair aired 15 “exclusive” interviews with Donald Trump — and none with Hillary Clinton — after Trump’s son-in-law, Jared Kushner, reportedly negotiated a deal to provide access in exchange for positive publicity. A Washington Post analysis found that Sinclair’s coverage demonstrated “a strong tilt toward Trump” that disproportionately portrayed him in positive terms “while often casting Clinton in an unfavorable light.” Sinclair executives whipped up loaded questions to be asked on air, such as: “[Clinton] has been repeatedly faced with previous questions of trust. Can a president lead with so many questions of transparency?”

After Trump’s election, Sinclair hired two Trump aides to provide pro-White House on-air commentary. The TV chain forced local news stations to broadcast language questioning whether the FBI had a “personal vendetta” against a high-level Trump adviser and fanned conspiratorial notions that the chief executive was the target of a conspiracy by “deep state” operatives in the CIA.

Sinclair’s unabashed shilling for Trump has been well-timed. The broadcasting behemoth is now lobbying the administration to greenlight a $3.9 billion merger that would add 42 local TV stations to the 173 that Sinclair already owns. This could be worth tens of millions of dollars in additional profits by giving Sinclair penetration into 72 percent of U.S. households in 46 states.

In many respects, Sinclair’s naked politicking is a throwback to American journalism in the 1800s, when partisan newspapers openly propagandized for one political party or the other and were then rewarded with spoils when their candidates were elected to office — usually in the form of patronage jobs or government printing contracts. But the $4 billion deregulatory payoff that Sinclair hopes to receive today is far more valuable than anything a struggling 19th-century editorial hack could have dreamed of.

Sinclair’s promotion of Trump is particularly insidious because it exploits the high levels of trust that TV stations have built up over the years by covering school board meetings, county fairs, local weather, hometown sports teams and other community affairs devoid of ideological taint. Unlike cable network Fox News, which is relatively open about its right-wing political agenda and markets its brand accordingly, Sinclair’s partisanship has been more subtly camouflaged by being mixed in with traditional local news fare. Indeed, most Sinclair viewers likely have no idea who owns the TV station they’re watching and wouldn’t recognize the name of the corporate chain if they were told about it.

It’s a common misconception that the network affiliation of a local station — ABC, CBS, NBC — is what matters most, since this is what stations publicize when they advertise their entertainment programs. But this relationship barely affects the content of local TV newscasts, as I know firsthand after 10 years as a journalist at local TV stations. Our network affiliation was irrelevant to how we reported the news. Only station owners and the managers they hired had the power to shape our coverage — and none ever tried to force us to run slanted editorial content the way Sinclair is doing. Such heavy-handed partisanship would have led to insurrections in the newsrooms where I worked.

A handful of Sinclair employees have protested the ideological screeds handed down by their corporate brass. But there’s a high price to pay for such acts of conscience. Sinclair is notorious for the draconian legal contracts it forces its journalists to sign, which impose financial penalties for quitting and gag ex-employees from speaking out against the company. Many staffers, with families to support and mortgages to pay, simply can’t afford to challenge to the $6 billion conglomerate.

Meanwhile, Sinclair’s chairman dines at the White House with the president and meets privately with Trump’s FCC chairman, Ajit Pai, who is working to find creative loopholes that will help Sinclair further expand its broadcasting empire.

So what if the airwaves are supposed to belong to the public? Who cares about the free flow of information or a diversity of editorial voices? After all, the president himself has already weighed in, congratulating Sinclair for attacking “fake news” and proclaiming that “Sinclair is far superior” to other TV networks.

What is to be done? The Federal Communications Commission should stop Sinclair from getting bigger — but it won’t. Congress should hold oversight hearings and thoroughly investigate — but it hasn’t. And the courts, so far, haven’t reined in Sinclair, either.

In other words, the usual checks on power have gone silent. Without making a sound, they’re all speaking in unison — just like Sinclair’s TV news anchors.