Just days before a likely crowd of thousands inevitably converges on Civic Center for the traditional 4/20 pot smokeout at 4:20 p.m., no one is sanctioned to wrangle the event.

The most recent applicant for a public-assembly permit for Monday backed out this week, citing costly conditions from the city that were aimed at providing sanitation and safety for the crowd.

So on Thursday, Denver Parks and Recreation officials started late talks with the lead organizer of this weekend’s large 4/20 festival, which also will be at Civic Center. They offered the possibility of allowing him to have a stripped-down rally Monday.

Granting an assembly permit, which probably won’t come until Friday, would give the organizer some responsibility for the park and control over an anticipated gathering that the city estimates could top 25,000. The lack of a permit would mark a return to the ragtag conclaves of several years ago, before the 4/20 fest organizers upgraded it to a permitted event.

There is extra intrigue in the latest turn of events.

Weekend-festival organizer Miguel Lopez originally had asked to expand the event to three days, ending Monday. But months ago, parks officials turned down his request because of a moratorium this year on new or expanded events at major parks, including Civic Center.

Lopez opted to keep the two-day festival on the weekend, even though the April 20 date celebrated as a holiday by pot enthusiasts falls on a Monday this year.

But after two other applications for a Monday rally fell through — with one denied last month and the other withdrawn Wednesday — a parks staffer e-mailed Lopez on Thursday.

The message: You can apply to fill the gap.

Lopez did so quickly. He said Thursday afternoon that he still was negotiating with parks officials but had agreed to ax some elements for Monday that the weekend festival will have, including stages, merchant sales and vendor booths.

Having those elements Monday would be the easiest way, he said, to recoup organizing costs.

“We’re looking at probably close to $10,000 to $12,000,” Lopez said, to cover trash collection, fencing around the Greek Amphitheater where musicians would perform and servicing of portable toilets after the two-day festival to prepare for attendees of Monday’s rally.

Without vendor booths, Lopez said, he probably still could sell banner space and sponsorships and will be able to collect donations on site.

He said he was submitting a revised application to reflect officials’ requests for a pared-down event.

Parks and Rec spokesman Jeff Green confirmed the conversations and said Monday’s event must be a simpler free-speech rally because it would fall under a public-assembly permit.

The weekend festival has broader license, officials have said, because it was granted a fee-based special-event permit, finalized Wednesday.

Green says parks officials may not decide on Lopez’s new Civic Center permit request until Friday, after he provides documentation confirming his arrangements.

Until Wednesday, Anton Marquez, who has worked with Lopez on past events, had been negotiating with the city for a Monday assembly permit for weeks.

But he says he withdrew his application in frustration over the city’s unwillingness to allow vendor booths to recoup the cost to abide by the city’s requirements. In addition to portable toilets, those requirements included emergency medical arrangements, crowd monitors, trash cleanup and a site plan.

To Marquez, those conditions amounted to “a prohibitory tax on the event because of its historical status” as an attraction for big crowds.

Instead, he has decided to focus his efforts on launching a new series of rallies in Civic Center on the 20th of each month, starting in May. He wants to draw together artists and politicians to put the spotlight on the need for better marijuana policies, along with other health and education issues.

While others were applying for the now-scuttled pot-related events at Civic Center on Monday, Lopez obtained a rally permit across the street on a smaller state property, in the park between Broadway and Lincoln Street, closer to the Capitol.

But he’s mindful that the Civic Center park offers the chance for a larger event.

Lopez’s weekend festival, billed as the world’s largest 4/20 rally, has a musical lineup of ganja-friendly artists, including rapper Rick Ross on Sunday.

Denver police have issued public-consumption tickets at past 4/20 events in Civic Center, although not in wide-scale crackdowns. Police have said their focus is mostly on the crowd’s safety.

“We are expecting people on Monday (in Civic Center),” department spokeswoman Christine Downs said, “and we will staff accordingly. We will use discretion (in ticketing), as we have in years past.”

An unknown factor is how the April 20 pot holiday falling on a Monday will affect crowd size.

There are also competing pot-related events, including the U.S. Cannabis Cup, sponsored by High Times magazine, which runs Saturday through Monday at the Denver Mart in Adams County.

Staff writer Tom McGhee contributed to this story.

Jon Murray: 303-954-1405, jmurray@denverpost.com or twitter.com/JonMurray