At least 20 people were arrested in clashes in Washington on Saturday.
Videos have emerged of apparent Antifa or Black Lives Matter agitators attacking purported supporters of President Trump.
The attacks took place after dark, following peaceful, large-scale demonstrations by Trump supporters during the day.
In one incident, a middle-aged man was alone as he was targeted by a mob, who pushed him to the ground, then stomped on his head.
Other brawls and a stabbing occurred, leaving the victim in critical condition.
