Just how divisive are San Francisco’s housing politics? Look no further than the brewing war over in-law units.

A little context: All the politicians want in-law units. They think they’re an easy way to bring much-needed housing to the market and open up a few more places for people to live.

The question is: What kinds of regulations should in-law units be subject to? And on that topic, well, the politics are likely to get so heated you might think it’s a fight about your in-laws rather than in-law units.

On Tuesday, moderate Supervisors Mark Farrell and Scott Wiener introduced legislation that would legalize the construction of rent-controlled in-law units. The ordinance is a counter to one introduced in March by progressive Supervisor Aaron Peskin that seeks to do the same thing.

The difference, Farrell said, is that their legislation provides more incentives to build more units more quickly than Peskin’s ordinance.

“Our legislation will not only increase the number of rent-controlled units in San Francisco, but also expedite the building process to ensure we take immediate steps to tackle the housing crisis which exists today in every neighborhood,” Farrell said in a news release.

The release highlighted some of the differences in the two ordinances.

Peskin’s proposal would allow one in-law unit in buildings that have 10 units or fewer, and two in-laws in buildings with more than 10 units. Farrell and Wiener’s legislation would allow a maximum of two in-laws in buildings that have four units or fewer and has no cap for buildings that are bigger than that.

Their legislation would also allow for the construction of in-laws that could reduce ground-story retail or commercial space by 25 percent. Peskin’s legislation prohibits any reduction of commercial space.

Technically known as accessory dwelling units, in-laws are residential units added to an existing building, usually developed out of a garage or storage space.

Farrell’s office estimates that his legislation could “potentially” create 1,000 more units than Peskin’s.

Both ordinances ban the use of in-laws for short-term rentals.

“The more, the merrier,” Peskin said. “I am delighted that there is so much interest from my colleagues and look forward to coming up with the optimal piece of consensus legislation.”

Both proposals are headed to the Planning Commission in the coming weeks.

— Emily Green

Not so fast. That’s essentially what the city’s elections chief has told the organizers of an effort to recall Mayor Ed Lee.

The backers of the recall effort stopped by the Department of Elections Tuesday afternoon to submit a recall petition so they could begin collecting signatures to get it on the November ballot. They were met by Department of Elections Director John Arntz, who refused to accept it.

Arntz told them that under the city charter no recall petition can be initiated for “an officer who has held office for less than six months.”

The city attorney’s office has interpreted that to mean six months of the term the politician is serving. In other words, even though Lee has been mayor for five years, he won’t meet the six-month mark until July 8, six months after he was inaugurated for his second full term in office.

Waiting until then to submit the recall petition makes the possibility of it qualifying for the November ballot nothing less than a moonshot.

That’s because the mayor has seven days to craft a response, and the Department of Elections has 10 days after that to review the petition forms to make sure they’re appropriate. Which means the recall backers could have a total of two days to collect 46,700 valid signatures by July 26 — the deadline for qualifying measures for the November ballot.

David Carlos Salaverry, a remodeling contractor and 2014 candidate for District Six supervisor who is helping lead the recall effort, said the city attorney’s interpretation of the charter is wrong.

“We are definitely going to challenge it, and we hopefully will be in court within the next week or two weeks,” Salaverry said.

He said his collaborators in the effort are Mike Murphy, who championed the unsuccessful 2014 ballot measure to prevent the installation of artificial turf soccer fields at Golden Gate Park, and 2015 mayoral candidate and musician Francisco Herrera, who placed second in the mayoral race.

Salaverry said their preference is to get the measure on the November ballot because of the expected big turnout.

“We don’t want to have a special election, but if that’s the way we got to go we will go that route,” he added.

— Emily Green

Emily Green is a San Francisco Chronicle staff writer. Email: cityinsider@sfchronicle.com, egreen@sfchronicle.com Twitter: sfcityinsider @emilytgreen