WASHINGTON (AP) — Fervent supporters of President Donald Trump rallied in Washington on Saturday behind his spurious claim of a stolen election and swarmed his motorcade in adulation when he detoured for a drive-by on his way out of town.

Hours later, after night fell in the nation's capital, demonstrators favoring Trump clashed in the streets with counterprotesters, videos posted on social media showing fistfights, projectiles and clubs. Police arrested at least 20 people on a variety of charges, including assault and weapons possession, officials said. One stabbing was reported, two police officers were injured and several firearms were also recovered by police.

A week after Democrat Joe Biden was declared the winner of the election, demonstrations in support of Trump also took place in other cities. Fury at the prospect of a transfer of executive power showed no signs of abating, taking a cue the president’s unrelenting assertion of victory in a race he actually lost.

“I just want to keep up his spirits and let him know we support him,” one loyalist, Anthony Whittaker of Winchester, Virginia, said from outside the Supreme Court, where a few thousand assembled after a march along Pennsylvania Avenue from Freedom Plaza, near the White House.

A broad coalition of top government and industry officials has declared that the Nov. 3 voting and the following count unfolded smoothly with no more than the usual minor hiccups — “the most secure in American history,” they said, repudiating Trump's efforts to undermine the integrity of the contest.

In Delray Beach, Florida, several hundred people marched, some carrying signs reading “Count every vote” and “We cannot live under a Marxist government.” In Lansing, Michigan, protesters gathered at the Capitol to hear speakers cast doubt on results that showed Biden winning the state by more than 140,000 votes. Phoenix police estimated 1,500 people gathered outside the Arizona Capitol to protest Biden's narrow victory in the state. Protesters in Salem, Oregon, gathered at the Capitol.

The crowd in Washington was beginning to gather Saturday morning when cheers rang out as Trump's limousine neared Freedom Plaza. People lined both sides of the street, some standing just a few feet away from Trump’s vehicle. Others showed their enthusiasm by running along with the caravan.

They chanted “USA, USA” and “four more years,” and many carried American flags and signs to show their displeasure with the vote tally. After making the short detour for the slow drive around the site, the motorcade headed to the president’s Virginia golf club.

Among the speakers was a Georgia Republican newly elected to the U.S. House. Marjorie Taylor Greene, who has expressed racist views and support for QAnon conspiracy theories, urged people to march peacefully toward the Supreme Court.

The marchers included members of the Proud Boys, a neo-fascist group known for street brawling with ideological opponents at political rallies.

The march was largely peaceful during the day before turning tense at night, with multiple confrontations as small groups of Trump supporters attempted to enter the area around Black Lives Matter Plaza, about a block from the White House, where several hundred anti-Trump demonstrators had gathered.

In a pattern that kept repeating itself, those Trump supporters who approached the area were harassed, doused with water and saw their MAGA hats and pro-Trump flags snatched and burned, amid cheers. As night fell, multiple police lines kept the two sides apart.

Videos posted on social media showed some demonstrators and counterdemonstrators trading shoves, punches and slaps. A man with a bullhorn yelling “Get out of here!” was shoved and pushed to the street by a man who was then surrounded by several people and shoved and punched until he fell face first into the street. Bloody and dazed, he was picked up and walked to a police officer.

The “Million MAGA March” was heavily promoted on social media, raising concerns that it could spark conflict with anti-Trump demonstrators, who have gathered near the White House in Black Lives Matter Plaza for weeks.

In preparation, police closed off wide swaths of downtown, where many stores and offices have been boarded up since Election Day. Chris Rodriguez, director of the city’s Homeland Security and Emergency Management Agency, said the police were experienced at keeping the peace.

The issues that Trump’s campaign and its allies have pointed to are typical in every election: problems with signatures, secrecy envelopes and postal marks on mail-in ballots, as well as the potential for a small number of ballots miscast or lost. With Biden leading Trump by wide margins in key battleground states, none of those issues would have any impact on the outcome of the election.

Trump’s campaign has also filed legal challenges complaining that their poll watchers were unable to scrutinize the voting process. Many of those challenges have been tossed out by judges, some within hours of their filing.

A former administration official, Sebastian Gorka, whipped up the crowd by the Supreme Court by saying, “We can win because he did win.” But, he added, “It's going to be tough.”