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. The event ... 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 ... 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 protest against the government. 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. 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.