SPRINGFIELD — Under the Illinois constitution, a binding statewide referendum question must be approved at least six months before the next general election. This places Illinois lawmakers’ 2026 deadline at May 3 — one month from today.

In the past decade, questions included whether to establish a lockbox for transportation funds, enshrine the right to collectively bargain and change the state’s income tax from a flat to graduated structure.

The first two were approved by voters while the last, on the ballot in 2020, was rejected.

But there’s been chatter about placing a variation of the graduated income tax on this year’s ballot. The proposal calls for a 3% surcharge on income over $1 million, mirroring the language of an advisory referendum question on the 2024 ballot that won 61% support.

Proponents suggest the revenue from this “millionaires tax” could be set aside for property tax relief, K-12 education funding or both. It has a powerful backer in House Speaker Emanuel “Chris” Welch, D-Hillside, who told Capitol News Illinois in February that he’s working to build support for the amendment, which would need supermajorities in both the House and Senate to secure a place on the ballot — but not a signature from the governor.

Former Gov. Pat Quinn has also been pushing the effort from the outside.

Lawmakers have been reluctant to revisit the issue since the 2020 failure. And strong revenue numbers buoyed by post-pandemic economic activity and federal stimulus funds made it easier than expected for lawmakers to balance the budget in the years that followed.

But with the federal government slashing funding to states and enacting tax policy changes that disproportionately benefit the wealthy, a millionaires tax is increasingly viewed as a populist pitch to recoup some of those lost dollars. It’s been enacted for years in California and New Jersey and, most recently, in Massachusetts and Washington.

A study published this week by researchers at the Illinois Economic Policy Institute and the University of Illinois at Urbana-Champaign lays out some of the potential benefits of a millionaires tax for Illinois.

The report, authored by ILEPI’s Frank Manzo and UIUC professor Robert Bruno, found that a 3% surcharge on income over $1 million would generate $3.8 billion in its first full year and $4.2 billion by 2030 — revenue estimates the researchers labeled as “conservative.”

The study by the left-leaning think tank explores three options for spending the cash: dedicate it entirely to property tax relief, fully fund the state’s Evidence-Based Funding formula for K-12 schools or a hybrid approach that’d freeze property taxes for schools while increasing education funding.

Under Option 1, Illinois could deliver $1,500 rebates to about three million homeowners who are eligible for and claim homestead exemptions. This would cut property tax bills for those folks more than 20% by 2030. This would still be a relatively small dent, moving Illinois from the eighth-highest property tax bills in the nation to 14th-highest. The state’s rates would go from second highest to sixth highest.

Option 2 would increase the state’s annual contribution to K-12 schools by more than $3 billion. Lawmakers have slowly increased annual education spending by $2.5 billion since EBF was enacted in 2017, typically with a minimum $300 million increase year-over-year. At that rate, school funding adequacy wouldn’t be achieved until 2039. But under this plan, it would be done in 2028.

It would also leave funds left over, which researchers suggest could be used for property tax rebates.

They predict that the increased EBF would indirectly stem the rise in property taxes by accelerating the shift in the funding burden to the state.

The third option suggests enacting an eight-year school property tax freeze and an education funding ramp that would achieve adequacy under Evidence-Based Funding by 2035. This would be done by applying the state’s property tax extension limitation law to all school districts and covering annual inflationary increases with millionaires’ tax receipts. It would also boost annual EBF contributions by $50 million every year through 2035. Researchers estimate this option would reduce property tax bills nearly 7% by 2030.

The report found that millionaires taxes in other states did not noticeably hurt economic growth or lead to significant outmigration among high earners. And any of the scenarios would have the effect of making Illinois’ tax structure less regressive.

The state’s high property taxes have long been a sore subject, with frustration cutting across political and geographic lines. Property taxes are imposed locally but intrinsically linked to state policy, most notably decades of underfunding K-12 schools. School districts make up more than half of a typical property tax bill.

Gov. JB Pritzker told reporters in Chicago earlier this week that school boards “didn’t take the hint” to keep their property taxes flat as they’ve received new state funding under EBF.

“And so, they’ve continued to ratchet up property taxes over and over and over again, and that has led to a continued very high property tax burden on homeowners across the state,” Pritzker said, adding that a millionaires tax “could” alleviate some of that burden, but wouldn’t do much on its own.

The governor was the chief proponent of the “fair tax” in 2020, but he’s made clear that another bite at the apple — whether a more traditional graduated structure or a millionaires tax — is not at the top of his agenda this year. It’s understandable. The 2020 initiative was arguably the biggest political loss in his seven years as governor.

That said, the chief opponent of that effort, venture capitalist Ken Griffin, is now a resident of Florida, and it’s unclear if he or anyone else would be willing to bankroll another opposition campaign.

On top of that, the political climate is far more favorable to Democrats heading into a midterm election with an increasingly unpopular President Donald Trump in the White House.

And while policy wonks will tell you that amendment language that just sets a rate structure is preferable to a millionaires tax enshrining a specific number, the latter is far easier to explain to people. And it would presumably be far easier to build a campaign around.

I have my doubts as to whether Democrats who control Springfield will place a millionaires tax on the ballot. But if they have the stomach for it, this might present their best opportunity to get a ‘rich-pay-their-fair-share’ amendment passed.

With significant budget challenges in the years ahead and property taxes remaining stubbornly high, I suspect that, at the very least, we will continue to hear about this idea.

Brenden Moore is a politics and government reporter for Capitol News Illinois, a nonprofit, nonpartisan news service that distributes state government coverage to hundreds of news outlets statewide. Moore in Springfield is his regular analysis column.