There are four vacancies on Philadelphia City Council, and more could be coming. Here’s what happens next.

Four Philadelphia City Council members have resigned in the last month — three in the past week quit to launch campaigns for mayor. And their timing is no coincidence.

At-large Councilmember Derek Green and Councilmember Maria Quiñones-Sánchez, of the 7th District, both resigned Tuesday and announced they’re running for the May 2023 Democratic primary for mayor. Councilmember Cherelle L. Parker, of the 9th District, resigned Wednesday for the same reason. Last month, at-large member Allan Domb gave up his seat and said he’s also considering a mayoral bid.

Because Philadelphia’s Home Rule Charter requires city officeholders quit their current post when they run for another office, there could be a half-dozen vacancies on the city’s legislative body in the coming months.

Part of the reason there were multiple resignations this week has to do with the way vacancies on Council are filled, a process that allows for members help hand-pick their own successors. Here’s a breakdown of what happens when there are openings on City Council:

The legislative body is set up to have 17 members — 10 represent geographic districts, and seven represent the city at-large. Of those seven at-large seats, two are generally reserved for members of political parties outside the majority.

Under the city charter, vacancies on Council may be filled via a special election, and the winner would serve out the remainder of the term. The terms of the recently resigned Council members would have ended in January 2024.

That’s complicated in some ways because all 17 seats are up for election next year, and those terms would begin in January 2024. That means the winner of a special election to fill open seats would serve fewer than 18 months, even if a special election were held quickly.

It’s up to the City Council president to decide when to call one, and that person — in this case, Council President Darrell L. Clarke — has wide latitude for when to do so.

Under most circumstances, these special elections are conducted during an already scheduled primary, general, or municipal election to save the city money and resources. This year, the general election is on Nov. 8. There’s no rule in the charter regarding how long a Council president can wait to issue a writ for a special election after a vacancy occurs.

There is precedent for waiting months. A special election to replace at-large Councilmember David Cohen was held in November 2006 — more than a year after he died. Then-Council President Anna C. Verna had opposed filling the seat, saying the duties could be absorbed by the six remaining at-large members.

No. Clarke is known to keep his decision-making process close to the vest.

But Clarke would likely have to issue writs of election this week to add races to the November ballot, because election officials need time to print and distribute mail ballots.

» READ MORE: What is Philly’s resign-to-run rule?

Under the city charter, the Council president is supposed to call for one at least 30 days in advance of the election. But that rule, written decades ago, probably does not provide enough time.

The Pennsylvania Department of State offers a process where voters can request, fill out, and turn in an absentee ballot in one visit to an election office. That is supposed to be available 50 days before an election.

In addition, a large portion of the city now votes by mail, and those ballots need to be prepared and mailed out as early as possible to give voters time to receive, vote on, and return them. As soon as candidates are finalized, elections officials rush to print and mail the ballots.

The political parties put forth nominees, and the method for choosing those are outlined in each party’s bylaws.

Because registered Democrats dramatically outnumber Republicans in Philadelphia, the person the Democratic Party nominates almost always wins the election.

It’s generally considered more urgent for district Council seats to be filled, because those offices handle a large volume of constituent services. The Democratic nominee is chosen by ward leaders who represent the areas within that district and, as tradition has it, the outgoing Council member has great sway in who they choose.

Quiñones-Sánchez said she hopes Clarke will order a special election to fill her seat that would coincide with the Nov. 8 general election for state and federal races. She is backing her former chief of staff, Quetcy Lozada, to replace her, and given the district’s heavily Democratic electorate, Lozada would almost certainly win the election to finish Quiñones-Sánchez’s term if she is nominated.

Parker declined to comment on who she’s backing to take her spot.

At-large candidates, who represent the entire city, are chosen by the party’s city committee, which is made up of the leadership of the party and its ward leaders.

» READ MORE: The 2023 race for Philly mayor is starting soon. Meet the candidates who might run.

It’s unclear if Clarke will call for special elections to fill those seats. At least two other at-large council members besides Domb and Green — Democrat Helen Gym and Republican David Oh — are rumored to be considering running for mayor and would have to resign their Council seats to declare candidacy, leaving potentially two more vacancies.

Staff writers Jonathan Lai contributed to this article.