Illinois Gov. JB Pritzker is facing a political buzzsaw on the subject of political mapmaking, that once-every-decade, winner-takes-all process where the party in charge of the legislature gets to draw new political boundaries.

It’s a high-stakes deal that governs which party likely will get to control the Illinois Senate and House for the next five election cycles through 2031. And with that prize comes big policy implications.

In 2018, as a candidate for governor, Pritzker railed against the time-honored process where the party in charge of the legislature controls the redistricting process. Whoever has the power to draw legislative and congressional districts does so in the most favorable way possible to win elections during the upcoming decade.

In response to a 2018 questionnaire from Illinois political blogger Rich Miller and author of “Capitol Fax,” Pritzker vowed to veto any new legislative maps that were drawn by legislators, party leaders or their staffs. The governor-to-be also advocated turning political apportionment over to an independent commission.

It was an absolutist stance that the governor this week appeared to move away from.

“I will veto an unfair map. I’ve also said that in order for us to have an independent commission we needed to have a constitutional amendment, something that would actually change the way the process operates today in the Constitution,” the governor said Tuesday. “That did not happen so now as we reach the end of the session and I look to the legislature for their proposal for a redistricting map, I’ll be looking to it for its fairness, and that’s something that’s vitally important for our state [and] has an effect on the next 10 years on representation throughout the state.”

The devil is in the details about what would constitute an “unfair map” to the governor. He didn’t say. But he made clear that he’s no longer of the mind that the old way of doing things when it comes to political mapmaking is necessarily all that bad.

Republicans pounced on the governor’s apparent backtracking, calling his evolving stance an outright flip-flop that betrayed his words as a candidate.

“It is time that Gov. Pritzker kept his promise that he has made over and over again to the people of Illinois, and that promise is to support an independent map process for redistricting,” said Senate Minority Leader Dan McConchie, R-Hawthorn Woods.

Democrats have held dozens of redistricting hearings around the state, including two more scheduled by a Senate redistricting panel on Saturday [May1] at Malcolm X College and Chicago State University. The hearings will be broadcast live at 10:30 a.m. and 5 p.m. Saturday at www.ilga.gov.

The chair of that committee, state Sen. Omar Aquino, D-Chicago, said he intends to gather as much citizen input as possible before turning to the task of drawing up legislative maps.

“The process we’re going through has been the most open one and successful one that I think the state has ever had,” Aquino said.

But reform groups claim the hearings held so far have not drawn many people, in part, because most of them have been held in the middle of the work day for many Illinoisans.

“Both the House and Senate have had record numbers of hearings, and I’m sure we’ll hear all about that and how terrific that was, but I’d make an educated case that 90 percent of them have been held during most people’s working hours, and very little has been done to publicize or advertise them,” said Madeleine Doubek, executive director for Change Illinois, a government-watchdog that has urged redistricting reforms.

“It’s the equivalent of a tree falling in the forest and no one hearing,” she said.

The legislature’s scheduled spring adjournment is May 31. Aquino said it is not clear when the public will get a first look at his committee’s handiwork during the coming weeks, but he promised the eventual legislative maps would be fair and give communities of color the representation to which they’re entitled.

As the process unfolds, here are a few bullet points about how redistricting works and what it all means.

What is redistricting?

The Illinois constitution requires the state legislature every decade to draw political boundaries for legislative districts, and the legislature also draws congressional boundaries. The last time it was done was in 2011. There are 59 Senate districts, 118 House districts and 17 congressional districts the Democratic-led legislature will be reshaping.

When does it have to be finished?

The state constitution dictates a June 30th deadline for the General Assembly to complete legislative redistricting but is silent on any deadlines for congressional maps. If a stalemate erupts and that deadline is blown, an eight-member commission is formed and has until Aug. 10 to draw political boundaries. If no consensus emerges, then there is a drawing by Sept. 5 to decide which party controls the process. The last time that happened was in 2001. This time, Democrats are expected to rally around a map that Pritzker will sign, leaving Republicans as mere spectators to the process.

How does the legislature draw political maps?

Despite the public face of hearings, the actual act of drawing political boundaries is a traditionally secretive process tightly guarded by the majority party in control. Doubek recalled how in 2011, Democrats didn’t reveal or vote on legislative maps until the final hours of the spring legislative session.

“Nobody had a chance to understand what was happening or respond to the maps that were unveiled, and within 24-36 hours, they were voted on by the House and Senate and were approved,” she said. “That’s not transparency or participatory democracy.”

The constitution says the districts are supposed to be drawn in a manner that is “compact, contiguous and substantially equal in population.” It’s supposed to reflect population shifts from one community to another and the overall demography, but there’s also opportunity for political mischief by the party in charge.

For example, in 2011, in a certain act of Democratic skullduggery, four incumbent House Republican members were put into the same House district. It forced two of them to move, and two others ran for the state Senate.

And there also are extreme acts of cartographical gymnastics in order to boost the fortunes of a particular candidate. The 4th Congressional District, now occupied by U.S. Rep. Jesus “Chuy” Garcia, D-Ill., was named by the Washington Post as one of the nation’s most gerrymandered congressional districts.

What’s at stake in the process?

Democrats control the process this year and did so in 2001 and 2011. It’s no coincidence that Democrats went on to win five-out-of-five election cycles during each decade as it built up supermajorities over Republicans in the House and Senate during that time. Republicans last controlled the process in 1991. Despite that advantage, House Democrats under former Speaker Michael Madigan won four out of five elections during the following decade.

What happens with congressional maps?

Democrats hold 13 of the state’s current 18 congressional seats. But a slight dip in population since 2010 means Illinois will lose a congressional seat. Democrats are expected to draw boundaries in a way that might expand on the party’s one-sided margins over Republicans. That would help Democratic House Speaker Nancy Pelosi maintain a Democratic majority and offset expected GOP pick-ups in Sun-Belt states that gained congressional seats.

What are the points of contention?

Besides what party should control the process, there is an argument over what data should be used as a basis for drawing the maps.

Traditionally, U.S. Census data is made available during the spring. But this year, because of the pandemic and a slow start to the headcount by former President Trump’s administration, Illinois and other states won’t get granular Census data until late September. That means Democrats drawing legislative boundaries are expected to rely on Census estimates from last year that proved to be off by more than 200,000 people statewide compared to the actual count.

The state constitution doesn’t specify actual Census data has to be used in redistricting. However, Democrats likely will wait until the fall to approve a congressional map so detailed Census data can be used, minimizing the chances of litigation that could impact control of the U.S. House.

Dave McKinney covers Illinois politics and government for WBEZ. Follow him on Twitter @davemckinney.