A few hundred protesters gathered around the US Capitol on Saturday, for a rally in support of the pro-Trump rioters who ransacked the building on 6 January.
But the group were easily outnumbered by the police and journalists present.
Ahead of the event, police said they had detected "threats of violence" and security was tightened in Washington.
Organisers had a permit for 700 to attend, but only about 100 to 200 protesters turned up, Reuters reports.
Capitol Police said 400 to 450 people were inside the protest area - but that figure included the heavy media presence.
Washington police officials had been expressing concern about the "Justice for J6" event for weeks.
Its organisers - Look Ahead America - were led by Matt Braynard, the former director of data and strategy for Donald Trump's successful 2016 campaign.
Hundreds of officers patrolled the Capitol grounds and 100 National Guard troops were on standby.
A fence was erected around the Capitol, and lawmakers were advised to avoid the area.
Speakers at the rally insisted that hundreds of rioters arrested for their actions on 6 January were "political prisoners" who had committed no violence.
About 600 people have been charged in the federal investigation into the Capitol riot, where a pro-Trump mob tried to stop the US Congress from certifying the 2020 election result.
At least 185 are accused of assaulting, resisting, or impeding police officers or employees. More than 70 were charged with destroying or stealing government property.
Most of those charged have been released ahead of their trials. The Associated Press news agency reports that about 63 are still in custody, citing court and jail records.
In July, officers who defended the Capitol during the riot told a Congressional committee they had been beaten and suffered racial abuse. One testified that he was knocked unconscious and suffered a heart attack. Another, an Iraq War veteran, compared the scene to a "medieval battlefield".
Tony Smith, 40, from Maryland, told Reuters news agency he had come to Saturday's rally to support a fair judicial process for those charged.
"If we don't honour that, we don't honour America," said Mr Smith, who carried a poster board reading: "We Want Trump!"
Some counter-protesters also gathered around the Capitol, carrying anti-Trump signs. One was removed by police after confronting the pro-Trump attendees.
Rally organiser Mr Braynard had repeatedly urged his protesters to remain peaceful. Earlier this week he also asked them to avoid wearing pro-Trump clothing or paraphernalia.
Mr Trump, for his part, said in an interview that he believed the rally would be "a setup".
"If people don't show up they'll say 'oh, it's a lack of spirit'," he told The Federalist, a conservative news outlet. "If people do show up, they'll be harassed."
Capitol Police said four arrests were made, including a person in the crowd who was carrying a knife, and a man reported to be carrying a handgun.