Redistricting rarely goes smoothly for Philadelphia City Council.

The once-a-decade process of redrawing district lines based on new U.S. Census data has produced pitched political battles in the past — in 2001, one lawmaker threatened to throw another out a window. It’s also produced gerrymandered maps. Previous versions of two North Philadelphia-based seats, for instance, were widely seen as among the most bizarre and unfair local government districts in the country.

But this year, lawmakers and City Hall observers are predicting a smoother process, with minimal changes expected to the Council districts that were used in the 2015 and 2019 elections.

“I don’t foresee major, major changes,” said Councilmember Mark Squilla, whose 1st District, which stretches from the eastern half of South Philly to parts of the River Wards, grew faster than any other over the last decade and will have to shed constituents. “I think you’ll just see minor boundary changes.”

The new maps are enacted through legislation passed by Council and signed by the mayor. Members have until March 12 to adopt new maps, which would be used in the 2023 election cycle.

In Philadelphia, like many other jurisdictions, legislators draw their own districts. That’s why redistricting is often criticized as an opaque process in which politicians get to choose their voters, instead of the other way around.

The Committee of Seventy, a Philadelphia good-government advocacy group, has called for independent commissions to redraw district lines instead.

“For far too often and in far too many places, it is our elected officials who draw their own maps,” said Patrick Christmas, the group’s policy director. “It will continue to be important for permanent change to be made that puts the map-drawing power in the hands of residents.”

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But with such reform looking unlikely anytime soon, Christmas said Council can make its process more transparent with two improvements: publishing a draft map for residents to comment on well in advance of final passage and requiring lawmakers to publicly explain their decisions.

Joe Grace, a spokesperson for Council President Darrell L. Clarke, said there will be “ample opportunity for public comment.” He didn’t indicate there will be changes to the process this year.

“There will be a public process and input into redistricting, as is traditionally the case,” Grace said in a statement. “Council takes its duties on this topic very seriously.”

Despite being drawn behind closed doors, the current maps lawmakers produced a decade ago are seen as mostly fair, with communities largely grouped in reasonable districts. The 10th District, for instance, includes the Far Northeast, and the 3rd District is the heart of West Philadelphia.

“The good news is that the worst gerrymanders of the past were largely addressed in the last cycle,” Christmas said, pointing to the 7th District’s previously serpentine shape, which had the effect of diluting Latino voting strength in Kensington until it was redrawn. “Still, there are plenty of boundaries here that probably don’t make sense to the residents who live nearby.”

He pointed to a “peninsula” jutting out of Clarke’s central North Philly-based 5th District over to Olde Kensington and Fishtown, where Clarke lives.

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Mayor Jim Kenney, who was a Council member during the last redistricting cycle, helped craft the map that won the day in 2011, beating out a separate proposal backed by then-Council President Anna Verna. This time around, Kenney believes “minimal changes to the current districts need be made instead of a wholesale redrawing of the district boundaries,” Kenney spokesperson Deana Gamble said.

“The Mayor feels that much progress was made to make Philadelphia’s Council Districts more sensible and fair 10 years ago,” Gamble said in a statement.

Philadelphia has an unusual Council structure, with 10 members representing geographic districts and seven at-large members representing the entire city. While they are not affected by the outcome, at-large members get to vote on the district maps.

One quirk in this year’s redistricting is the potential that, for a variety of reasons, a relatively high number of district members may never represent the districts they draw.

Some, like Councilmembers Maria Quiñones-Sánchez and Cherelle L. Parker, are widely seen as eyeing the 2023 mayoral race. Under the city’s Home Rule Charter, they would have to resign their seats to run for the city’s top job.

Others may face tough reelection battles. Squilla, for instance, is a centrist Democrat and could be vulnerable to a challenge from the left. Much of his district has been fertile ground for the city’s progressive movement, which has won ward leader positions and even a state Senate district in Squilla’s South Philly backyard.

And some may retire. Clarke will be older than 70 by the next election and has been in office since 1999. Grace said Clarke will “consider his own political future ... at the appropriate time.”

Additionally, two district members, Bobby Henon and Kenyatta Johnson, are awaiting trial in unrelated public corruption cases. Both have denied wrongdoing.

Lawmakers typically protect themselves during redistricting. Vacancies could provide flexibility to mapmakers by freeing them of the need to consider incumbents’ addresses and voting blocs.

The Home Rule Charter requires lawmakers to draw districts that are as equal in population as possible, but there is no legal definition of how much variation there can be. Courts have traditionally approved maps if the least and most populous districts are within 10 percentage points of each other, Christmas said. That window is calculated by determining if any district’s population is 5% greater or lesser than one-tenth of the city’s overall population, or about 160,000 people.

The new census data show that four districts are now outside the window. Squilla’s district is now 7.2% larger than one-tenth of the city population and will have to get smaller in population, as will Clarke’s 5th District, which is 6.7% larger than average. On the other end of the spectrum, Curtis Jones’ 4th District, which includes parts of West Philadelphia and Northwest Philadelphia, is 8.1% below the benchmark and will have to grow. So will Cindy Bass’ 8th District, which is 6.2% below.

Those districts, however, also border other districts, and changing the lines of one will create a chain reaction causing all of the districts to be altered.

“I remember the back and forth numbers that we did the last time, and it was fascinating,” Jones said. “The what-ifs scenarios ran a mile a minute. If you move something 10 blocks one way or the other, it’s a different” citywide map, he said.

For Quiñones-Sánchez, who occupies the previously gerrymandered 7th District, this will be the fourth time she has worked on redistricting, either as a lawmaker or an advocate. This time, she’ll be happy if there are no major changes to her district.

“It’s nice not to be in the most gerrymandered district in the country anymore,” she said.

Staff writer Laura McCrystal contributed to this report.