An unusual trial scheduled to begin on Tuesday in Tampa, Fla., involves obscure candidates for local office, activist groups far outside the political mainstream and relatively little money changing hands.

But experts say it offers a rare glimpse into how Russia has tried for decades to secretly influence American politics.

Prosecutors say that Russia, in relatively low-tech fashion, sought out a sympathetic group in the United States, invited its leader to visit Moscow and established a long-term relationship through calls, email and electronic messages. The group, which has long had a presence in St. Petersburg, Fla., then promoted Russian views on its website, social media accounts and radio station. One post argued that Russian athletes should be allowed to participate in the 2016 Summer Olympics.

Four Americans face charges that they conspired to have other U.S. citizens act as illegal agents of the Russian government, or that they acted as unregistered Russian agents themselves. The prosecutors say that Russians directed them — and in some cases, paid them — to push Russian propaganda, including after their country invaded Ukraine in 2022.

The defendants, who have pleaded not guilty, say that the U.S. government is criminalizing dissent protected under the First Amendment. All four of them are current or former members of the African People’s Socialist Party, an organization promoting Black power; three are also members of the Uhuru Movement, the party’s activist arm, which is based in St. Petersburg and St. Louis.

One of the defendants also founded a different group, Black Hammer, a radical Black separatist organization in Atlanta. The Uhuru Movement supports self-determination for Black people and has protested issues from racism and colonialism to local police conduct for decades.