When a black church burned in Greenville, Mississippi, leaving charred walls and roof and the words “vote Trump” scrawled on the side of the building, local authorities called in the FBI. Its offices in Jackson, the state capitol, and Washington D.C. were put on the case.

The Federal Bureau of Investigation has been doing that kind of work for decades. It was the FBI, under pressure from Attorney General Robert F. Kennedy, that sent scores of agents to Philadelphia, Mississippi in June of 1964 to investigate the disappearance of three civil rights workers: Michael Schwerner, Andrew Goodman and James Chaney, who had themselves been investigating the firebombing of a black church that was to serve as a “freedom school,” in preparation for registering black Mississippians to vote. When the three men were found dead—lynched and discarded in an earthen dam—it was FBI agents who made the discovery, acting on an informant’s tip.

The FBI has had its dark days, too. It was the federal law enforcement agency, under director J. Edgar Hoover, that tried to harass Dr. Martin Luther King Jr. literally to death; and that infiltrated, sabotaged and set up members of the civil rights movement, anti-war movement, the Black Panthers, and more; from COINTELPRO to infiltrating and spying on groups opposed the 2003 invasion of Iraq. The most recent target of massive surveillance by the FBI: protest movements organized under the broad banner of Black Lives Matter, which collectively are aimed at reforming policing, to reduce often fatal violence against unarmed black civilians.

Americans have, at various times, leaned on the FBI for a measure of justice that local and state police couldn’t be counted on to deliver, and recoiled in fear at their exercise of raw federal power. That uneasy trust; the combination of need and dread, is the lot that FBI agents live with day to day.

The events of the past two weeks have made it all but impossible to have much faith in the FBI now. The agency has, through the actions of a minority cell of unknown size, been severely tainted, potentially dragging down the reputations of even the finest agents in its ranks.

After all, how can we trust the nation’s foremost federal law enforcement agency now that it has become clear that a faction of its agents used a conspiracy theory-hawking political book to launch a partisan probe into a presidential candidate?

That unprecedented prospect: that federal law enforcement could take it upon themselves to try and swing a national election using allegations gleaned from a partisan hatchet job financially linked to the target’s political opponent, is Third World stuff. It makes the already creepy chants of “lock her up!” at Trump rallies reminiscent of a spiraling coup d’etat in a banana republic, because clearly, some in the FBI want to make those chants come true. And it makes Rudy Giuliani’s assertion, two days before Comey’s vague oppo dump, that the campaign had “a couple of things up our sleeve to turn [the race] around,” an ominous tell indeed.

Most Americans presume that members of law enforcement tend to be ideologically conservative. But many Americans have watched in alarm as police officers across the country pose with the Republican candidate, even donning red “Make America Great Again” baseball caps with their police uniforms. Those acts, often criticized by the officers’ superiors, convey a clear message to people of color that the cops stand with Trump—the promoter of nationwide “stop and frisk,” whose “New Deal for Black America” is more police in our communities, unleashed to bring old fashioned, Nixonian “law and order.”. These officers clearly don’t mind if those they police know that they concur with Trump’s divisive, racially abusive message, which excludes and threatens black, Hispanic and Muslim Americans; not to mention women and members of the media. That doesn’t surprise many people of color. But it’s no less chilling, knowing that people sworn to “protect and serve” share Trump’s worldview.

FBI agents are, presumably, drawn from much the same pool as law enforcement generally: mostly white, mostly male, mostly right of center. If the agency is indeed, “Trumpland,” as The Guardian’s Spencer Ackerman reports, God help Hillary Clinton. But God help the rest of us well. We want to believe that the agents investigating that church burning in Mississippi have more sympathy for the black parishioners than for the ideology of the man whose name was scrawled on the wall. The FBI, to be credible with the American public, needs us to.

We have entered an unprecedented new age when federal law enforcement demonstrates a willingness to go beyond each agent exercising his or her individual right to vote to massing its investigative powers against an individual for political purposes. That the FBI could become a tool in the arsenal of one party’s presidential candidate, perhaps even coordinating with that candidate through their mutual allies, is the most frightening development in a truly unnerving presidential cycle. It should be unnerving to their fellow FBI agents as well, and to anyone who cares about the agency’s reputation.

It compounds the calamity of last week’s “October Surprise” from FBI director James Comey, who threw a grenade into the middle of the presidential race eleven days out, with a vague letter casting aspersions on Hillary Clinton without evidence of wrongdoing. Clinton, after all, is not only Trump’s opponent; she’s the longtime nemesis of one of his key surrogates, Rudolph Giuliani, whom Clinton initially faced as an opponent for the U.S. Senate.

Back then, in 2000, Mrs. Clinton inveighed against the extrajudicial killings of 22-year-old Amadou Diallo and 26-year-old Patrick Dorismond by undercover police, and Giuliani’s reflexive defense of the officers who killed them. She did so in terms that echo the calls of #BlackLivesMatter today, telling black New Yorkers that Diallo, a West African immigrant shot 41 times as he reached for his wallet in the vestibule of his Bronx apartment, would have been alive had he been white; and excoriating Giuliani for maligning Dorismond in death by releasing his juvenile record.

Giuliani’s allies in the NYPD hated her back then. Based on the reports from multiple journalists, including Wayne Barrett, some of Giuliani’s friends in the FBI hate her still. But should they be able to use the badges the public pins on them to try and prevent her from winning a presidential election?

Today, the New York division of the FBI is investigating Anthony Weiner, the pervy former Democratic congressman and estranged husband of top Hillary Clinton aide Huma Abedin. It is from there that Comey’s email bomblet emerged. New York field agents were investigating the death of Eric Garner, who was choked by officer Daniel Pantaleo on a public sidewalk in full view of several Staten Island police officers, for potential violation of Garner’s civil rights. But not anymore. The Justice Department recently replaced them with agents outside New York. Could the rancor over that case have further driven the division to mutiny?

Whatever the cause, it’s clear that there is a cancer festering inside the nation’s pre-eminent law enforcement agency, and it runs through New York.

The possibility that the director of the FBI is essentially at the mercy of a right-wing faction of his own agents, whose source of investigative material is an offshoot of Breitbart.com, which has direct connections to the Republican candidate, bodes ill for what the agency might do with its power, under either potential president. Would the Breitbart wing of the FBI continue to hunt the new Democratic commander in chief based on the thin gruel ladled out by fever swamp websites? Or would it become the investigative sword wielded by the Republican president against his political enemies, Democrat and Republican, any of whom could face investigation if they displeased him and his fans?

Either way, the result would not be democracy. It would be authoritarian tyranny of a downright Putinesque kind.

Something is rotten inside the FBI. Americans have good reason to be afraid, and angry.