DENVER -- What if they gave a protest and almost nobody came? Some are asking that question in Denver, where months of anticipation of mass protests during the Democratic National Convention have amounted to little so far.

Video: Protesters Arrested | Slideshow Of Protests

That could change with an anti-war concert by Rage Against the Machine on Wednesday and a planned march afterward.

Still, organizers had hopes for crowds numbering 5,000, 10,000, even 25,000 descending on Denver to draw attention to issues ranging from the war in Iraq to fuel prices to marijuana prohibition.

Authorities prepared for them. Denver police called in a uniformed force of about 1,000 additional officers from around the metro area and even horse patrols from out of state. The federal presence has been nothing short of overwhelming.

Authorities said there have been about 135 arrests related to the convention over three days.

However, one protest group is taking issue with the law enforcement. Saying any trust had been lost with police, organizers of the protest group Recreate 68 announced plans Tuesday to sue the City of Denver.

Mark Cohn, a co-founder of the group, said they are talking to attorneys about a lawsuit, reported KMGH-TV in Denver.

"The promise at the beginning of all of this was, 'We stay peaceful, they stay peaceful,'" said Glenn Spagnuolo, also a founder of the protest group. "That truce was violated."

Speaking through a bullhorn to reporters outside the Denver Police Department headquarters, the group's organizers accused police of illegally detaining and arresting people Monday night, when tensions escalated into a stand-off between police and protesters.

Denver police said it made limited use of pepper spray paintball-type bullets when the crowd, estimated at 300 people, refused requests to disperse.

Many were observed carrying rocks and other items that could be used to threaten public safety, according to a statement released Tuesday morning by Denver Police.

"Some individuals I represented in court had nothing to do with the protests at all," said Brian Vicente, executive director of the People's Law Project. "They were penned-in and were not allowed to leave."

Denver Police Lt. Ron Saunier defended the actions of police.

"Through the indications of a lot of things, we felt (the protesters) were getting ready to move down, start creating destruction of private property and possibly assaulting people," Saunier said.

Eighty-five people were arrested on charges of obstruction, disobeying lawful orders, and interfering with a police officer, Saunier said.

Police surrounded the area of 15th Street and Court Place out of concern for public safety, Saunier told KMGH Tuesday.

"We pretty much circled around (the demonstrators) and contained them within that area in an effort to de-escalate the situation, which it did," Saunier said.

Spagnuolo verbally fired back Tuesday, accusing police of whipping up tension with protesters in the hour before demonstrators donned bandannas and linked arms on Bannock Street.

"(Police were) pushing them with their feet, saying, 'Move out of my way,' instead of treating these people with respect," Spagnuolo said, adding the incidents occurred when much of the media was not around.

"They were building up that confrontation, and this is what it led to. It was totally unnecessary," Spagnuolo said.

"It became clear very early on, through the totality of all circumstances, that their intent was not to be there to express their First Amendment rights," Saunier said of the increased police presence in the park at that time.

"There's a lot of footage out there where officers were taking quite a bit of abuse and remained very professional," Saunier said.

Cohn disagreed and said the group is considering seeking $50 million in damages -- the same amount Denver was awarded by the federal government for security.

"We're not sure what was done with that money, but we think it's about time that some of the money go to people who've been victimized and whose civil liberties have been violated during this convention," Cohen said.