PORTLAND, Ore. — In the hours after President Biden’s inauguration this year, protesters marched once again through the streets of Portland, Ore., sending a message that putting a Democrat in the White House would not resolve their problems with a system of policing and corporate wealth that they saw as fundamentally unfair.
“No cops, no prisons, total abolition,” they chanted. Some of the activists, dressed in the trademark uniform of solid black clothing and masks that often signals a readiness to make trouble without being readily identifiable, smashed windows at the local Democratic Party headquarters.
The event — like others that had consumed the city since the murder of George Floyd by a police officer in Minneapolis in 2020 — included a variety of anarchists, antifascists, communists and racial justice activists. But there were others mingling in the crowd that day: plainclothes agents from the Federal Bureau of Investigation.
The F.B.I. set up extensive surveillance operations inside Portland’s protest movement, according to documents obtained by The New York Times and current and former federal officials, with agents standing shoulder to shoulder with activists, tailing vandalism suspects to guide the local police toward arrests and furtively videotaping inside one of the country’s most active domestic protest movements.
The breadth of F.B.I. involvement in Portland and other cities where federal teams were deployed at street protests became a point of concern for some within the bureau and the Justice Department who worried that it could undermine the First Amendment right to wage protest against the government, according to two officials familiar with the discussions.

Some within the departments worried that the teams could be compared to F.B.I. surveillance transgressions of decades past, such as the COINTELPRO projects that sought to spy on and disrupt various activist groups in the 1950s and 1960s, according to the officials, one current and one former, who spoke on condition of anonymity because they were not authorized to discuss the debate.
There has been no evidence so far that the bureau used similar surveillance teams on right-wing demonstrators during the Jan. 6 riot at the U.S. Capitol, despite potential threats of violence against the heart of federal government — though the F.B.I. did have an informant in the crowd that day. The bureau has at times used secretive tactics to disrupt right-wing violence, such as efforts that led to charges against men accused of conspiring to kidnap Michigan’s governor.