After eight days of protests in the District over the death of George Floyd in police custody in Minneapolis, officials are preparing for the week’s biggest demonstration in Washington.

Tens of thousands of protesters are expected in the nation’s capital Saturday in an all-out rebuke of aggressive police tactics, racism and the Trump administration’s militant approach to the days of unrest that have gripped cities from the District to Los Angeles and hundreds between.

Starting at 6 a.m. Saturday, police will close much of downtown to vehicle traffic, creating a pedestrian-only demonstration zone stretching between the southern boundary of the Mall and L Street NW to the north. The western boundary is along 19th Street NW, and the eastern edge is roughly Ninth Street NW through downtown and Third Street NW along the Mall.

A fortified perimeter around the White House, including a tall black fence that was erected late this week after days of volatile confrontations between police and demonstrators, will remain.

Unlike many other large-scale demonstrations that the District hosts, no one person or organization is leading Saturday’s events.

Nearly a dozen different demonstrations run by as many organizations or individuals have been advertised for Saturday, starting at 6 a.m. and running into the night. Many protesters plan to stay out until the early hours of Sunday morning.

There are no leaders to speak to and no agenda to follow.

Stages and podiums that are hallmarks of rallies such as the March for Our Lives and the Women’s March on Washington have given way to people with megaphones commanding the attention of nearby crowds.

For the past eight days, the protests have ebbed and flowed with the energy of the day. Demonstrators march from memorials to the White House and back again.

Even Black Lives Matter DC has repeatedly announced this week that it is not behind all the grass-roots activism that has taken hold and flooded the city with protesters. Online, people from around the Washington region and neighboring states announced their intention to join and encouraged others to do the same.

D.C. Police Chief Peter Newsham said no arrests have been made during protests since Tuesday. He said he hoped that that streak would continue as he expected on Saturday to see the largest crowd since protests began in the city on May 29.

“We anticipate the largest demonstrations with regards to numbers that we’ve seen in the city to date,” he said. “And we anticipate that the protesters will continue to be as peaceful as they have been over the past couple of days.”

In response to large crowds, Metro announced Friday that it will reopen the first and last rail cars on trains starting Saturday to boost capacity for rail riders.

The transit agency had kept the end cars closed on eight-car trains as a way to protect train operators from interacting with passengers during the coronavirus pandemic. Though operators work in enclosed compartments, the added buffer was a safeguard the transit union representing most of Metro’s workers had sought.

Opening the first and last cars is one of the few options Metro has to increase capacity, and officials said the move will be indefinite, not just for Saturday.

Though D.C. police and the National Park Service are preparing for tens of thousands of demonstrators, no one can say exactly how many to expect. Typical mechanisms used to gauge crowd size have been suspended or scaled back because of the coronavirus pandemic.

The Park Service has stopped issuing protest permits. Agencies that might typically discuss plans with community organizers have halted in-person meetings. Many administrative officials are working from home.

On Friday, D.C. Mayor Muriel E. Bowser (D) renamed a street in front of the White House “Black Lives Matter Plaza” and had the phrase “Black lives matter” painted in giant yellow letters along 16th Street NW near the White House.

The move, an escalation in Bowser’s feud with President Trump over control of D.C. streets, was meant to be a stark reminder to the president and legions of federal forces and military personnel called to the District amid the protests that the city’s allegiance is to “peaceful demonstrators,” said John Falcicchio, the mayor’s chief of staff.

Some D.C. residents and activists criticized the move as merely performative and demanded that the mayor follow up with substantive changes to the D.C. police department.

On Saturday, protesters planned to target city officials and buildings alongside those of the federal government with demonstrations in front of the U.S. Senate office buildings, the D.C. government’s Wilson Building, at Judiciary Square and Freedom Plaza, and the White House.

Officials said they expect demonstrations to be fluid and roaming, with groups breaking off to join other demonstrations as the day progresses and marches taking protesters through the city.

On Friday, crowds that jammed roads and flooded the White House for more than a week had eased into a jubilant rhythm.

Marches crisscrossed the District from the White House to Freedom Plaza and back again. Protesters arrived with speaker systems to play music and amplify the words of the Rev. Martin Luther King Jr. outside Lafayette Square, where peaceful protesters days before had been gassed, pepper sprayed and aggressively corralled by federal police.

“We aren’t going to let any Mace stop us,” King’s voice echoed through the air. “We are masters in our nonviolent movement in disarming police forces; they don’t know what to do.”

All around, demonstrators stood in silence, listening intently.

“It’s phenomenal,” said Jacqueline Stallworth, a 49-year-old teacher. “Everything he is saying is still relevant today.”

When the smoke grenades and pepper pellets started to fly earlier in the week at Lafayette Square, Kandyce Baker, 31, sat in front of the White House and prayed.

She returned Friday to a starkly different scene: The riot police were gone, the smell of chemicals no longer tainted the summer air, and a large fence encircled the park. Instead of facing the White House, as she did last time, Baker turned her back.

“I came here today … to be here where the people are,” she said.

Around her stood several hundred people as the sky darkened and a thunderstorm rolled in. Dancers hopped and grooved in the middle of the road as a crowd gathered to cheer — it was a street party as much as a protest.

“It’s amazing how all that has made people want to be out here with us even more,” said Aaron Covington, 26, a resident of Navy Yard who is organizing a rally Saturday at the Lincoln Memorial. “I’ve gotten messages from almost every state, people around the world, saying, ‘I wish I could be there with you.’ ”

The anger and sorrow that spurred demonstrations in the District and across the country this week was far from gone.

At the Justice Department, dozens of protesters marched on Pennsylvania Avenue chanting “No justice, no peace” while carrying a letter demanding the release of any demonstrators arrested this week.

At the Henry J. Daly municipal building, where a group of D.C. police officers stood guard, protesters called out the names of black men and women killed by police, including Breonna Taylor, the 26-year-old Louisville paramedic fatally shot in her apartment by police officers who were executing a drug warrant.

Some in the crowd then shared stories about their own encounters with police.

“I’m scared I won’t live long enough to have children,” said Terrence James, 26, before recounting how he and a group of friends were approached by police in 2017 at a Silver Spring 7-Eleven. Explaining that a robbery had just occurred, he said, the officers forced James and his black friends to lie facedown in the parking lot. They didn’t ask his white friend — who looked on in disbelief — to do the same, he said.

At Lafayette Square, demonstrators from outside the region had already begun to arrive.

Cindy Puentes, 24, stood outside the wire fence clutching a sign that said: “My husband’s black skin isn’t a crime.”

Puentes and her husband traveled hundreds of miles this week from their home in Kansas for Saturday’s demonstrations — and any that might follow. She plans to stay for three weeks, coming out daily to march.

“This is about my family,” she said. “I was tired of crying at home. … I’m tired of seeing so much hate everywhere.”

With a leaderless movement come challenges — not knowing who to follow or where to go, not having a preprinted list of slogans to chant along with as you march.

As night fell Friday, a crowd of protesters drenched in another evening thunderstorm tried to sync up as they wound their way toward the U.S. Capitol.

The group walked another block, but they still didn’t have it quite right.

“Use your ears,” a woman said, urging the few hundred gathered to try again.

“They say we can’t do this, they say we can’t organize,” she said. “Let’s show them we can do this.”

Fenit Nirappil, Julie Zauzmer, Michael E. Miller, Justin George, Emily Davies, Steve Thompson and Michelle Boorstein contributed to this report.