American schoolchildren learn at an early age that the federal government has three branches intended to check and balance each other: legislative, executive and judicial. Over the past two weeks, we have witnessed a fourth unelected branch assert its supremacy over all others: the police.

The protests that have swept U.S. cities began as a denouncement of police brutality. But what is happening in our streets has become a political power struggle over the legitimacy of democratic government itself. On one side are the police, asserting the right to ignore any command from democratically elected officials if they so please. On the other side are the people, demanding democracy and respect.

Police in city after city have made it very clear that they simply do not care if they are exposed as lawless brutes. On Thursday night alone, police in Buffalo, New York, shoved a 75-year-old man to the ground and left him motionless, blood spilling from his ear and pooling around him, while police in Indianapolis groped a womans breasts and beat her savagely with batons . Images of police cruelty and contempt for the law poured out of New York , Los Angeles , Chicago and several other cities .

The police violence is not restricted to Black protesters, or even protesters in general. On Saturday night, officers in Brooklyn brutalized a hospital worker walking home from his job of managing the COVID-19 crisis, leaving his hospital ID smeared with blood. Police are arresting journalists , legal observers and even food deliverers all of whom are permitted to be on the streets after locally imposed curfews just for doing their jobs.

All of these actions were not only outrageous, but flagrantly illegal, and dozens of similar horror stories are emerging every night. The police know the whole world is watching, and the message they are sending is very clear: Were in charge, not your laws or your elected officials.

This is authoritarianism. And it is disgraceful. Theres something profound about witnessing it erupt across the country around the anniversary of the 1989 Tiananmen Square Massacre in Beijing, where the Chinese government rolled out tanks and murdered thousands of peacefully protesting students. Police in U.S. cities today are not standing up for law and order they are expressing violent contempt for democracy itself.

For a long time, police have dismissed documented cases of abuse as the excesses of a few bad apples, insisting to the public that officers are generally an upright bunch who want to live in harmony with their communities. This crisis has rendered that excuse simply laughable. In dozens of cities, police are all doing the same things beating citizens for the sake of beating them, and publicly demonstrating their eagerness to flout the law and democratic will.

In the face of this assault on the nations democratic traditions, Democrats and Republicans alike have been exposed as either cowards or as figureheads without real power. On Thursday, New York Gov. Andrew Cuomo (D) publicly humiliated himself by denying that documented cases of police aggression had in fact taken place at all: Police bludgeon peaceful protesters with batons for no reason? Thats not a fact. They dont do that. Anyone who did do that would be obviously reprehensible if not criminal.

New York Mayor Bill de Blasio has been reduced to a laughingstock , drawing boos and jeers at public appearances where he carries on at length about his white privilege but refuses to take any substantive action to restrain New York police officers, who at least nominally report to him.

The grim fact is that police have historically exercised authoritarian dominion over Black neighborhoods all over the country. Whats been happening the last couple of weeks is an attempt by the police to expand their jurisdiction deeper into American life. As David Stein, a historian of mass incarceration at the University of California Los Angeles, observed : The police are extending their authoritarian jurisdiction from South Los Angeles and Skid Row, to everyone allied with the people of South LA and Skid Row. And it is happening in nearly every city, large and small, extending even into the pleasant, gentrified urban playgrounds of the upper-middle class.

Americans who were able to look the other way on police abuse for decades will not be able think about the police in the same way whenever this crisis eventually passes. The police are not only at war with mayors, governors, legislators and city councils they are at war with the American people and the very idea of America as a nation where citizens govern themselves.

For all of its very obvious flaws, the United States does have strong democratic traditions. Even the far-right fringe in our country uses the language of freedom, liberty and democracy to defend its values and ideas. Democracy in this country will not go down without a fight. But the only people who can save a democratic vision for America are the people themselves, in the streets, night after night. It is a fight they cannot afford to lose.

Zach Carter is the author of The Price of Peace: Money, Democracy, and the Life of John Maynard Keynes, available now from Random House .