Civic leaders and law enforcement are bracing for several groups of protesters to take to downtown Portland on Saturday for a planned right-wing rally and left-wing counterprotest that have been advertised for weeks. Here’s what you need to know.

What, exactly, is going to happen?

It’s hard to say. Portland’s largest protests tend to be roving, unpredictable affairs.

But here’s what we know:

Two Florida men with large followings in the right-wing movement are holding an “End Domestic Terrorism” rally Saturday at 11 a.m. in Tom McCall Waterfront Park.

An organizer said he expects up to 1,000 people show up for the event, which seeks to draw like-minded people from around the country as a show of force against self-described anti-fascists, or antifa.

Rose City Antifa, Portland’s homegrown, amorphous band of anti-fascist activists, is calling on supporters to turn out in opposition to the rally.

Myriad other events are scheduled, which are expected to draw hundreds of peaceful counter-protesters.

Who’s going to be there?

Former InfoWars staffer Joe Biggs is organizing the right-wing rally, and he’s getting help from Enrique Tarrio, national head of the Proud Boys.

Portlanders should expect a sizable showing of Proud Boys — whose members describe themselves as “Western chauvinists” and who often express disdain for Islam, feminism and liberal politics — and other right-wing figures.

They should also expect a large contingent of left-wing counterprotesters, including anti-fascists and other social justice activists at the center of Portland’s protest movement.

Joey Gibson — leader of right-wing Patriot Prayer, which has drawn widespread opposition during previous Portland demonstrations — has said he’s uncertain whether he will attend Saturday’s event.

Neither Gibson nor Patriot Prayer have been involved in promoting or organizing Saturday’s rally, and Gibson has largely shied away from demonstrations in Portland since being sued for his participation in a clash between right- and left-wing groups May 1 at Portland bar Cider Riot.

Gibson on Thursday announced that he was facing a felony riot charge in connection with the May Day incident. He told radio host Lars Larson that he was planning to turn himself in to authorities. As of 8 p.m. Thursday, authorities had not announced whether Gibson had turned himself in.

Some of Gibson’s supporters have launched an online fundraiser to help him with legal fees. As of Thursday evening, they had raised more than $5,000.

Gibson is the latest in a string of right-wing activists who have been arrested in the past week on felony riot charges related to the May Day brawl. Ian Kramer and Matthew Cooper were arrested on Aug. 7 and 8. Cooper was subsequently released. The two face charges related to beating a woman on the head with a baton — the alleged attack left her unconscious. On Aug. 13 and 14, Christopher Ponte and Mackenzie Lewis were arrested. Police and the district attorney’s office would not elaborate on the specific roles Ponte and Lewis allegedly played in the May 1 incident.

On Thursday, Cooper was arrested again, and another right-wing activist, Russell Schultz, was also arrested.

Oregon law states that a person can be charged with the crime of riot “if while participating with five or more other persons the person engages in tumultuous and violent conduct and thereby intentionally or recklessly creates a grave risk of causing public alarm.”

Conservative writer Andy Ngo, who was attacked by black-clad demonstrators in Portland earlier this summer, has not publicly said whether he plans to be at the demonstrations.

Video footage of the attack racked up millions of views online, generated days of national headlines and has helped create a surge of interest in Saturday’s rally.

What are police going to do?

Portland Mayor Ted Wheeler and Chief Danielle Outlaw have promised a large turnout by police and have vowed to use the full force of the law against those who commit acts of violence and vandalism. City officials have also been working with federal, state and local law enforcement agencies to secure the officers and equipment necessary to respond.

The mayor and chief also have gone on video and given interviews, pledging to do what it takes to keep the city safe during the demonstration and urging trouble-seeking participants to stay away from Portland.