CHICAGO (CBS) — Late Wednesday afternoon, Illinois Governor JB Pritzker sealed his biggest legislative victory.

He signed the bill to let Illinois voters decide on a graduated income tax. But it’s also the official kickoff to a war over taxes in Illinois.

CBS 2 political reporter Derrick Blakley explains what’s at stake in the big tax battle.

With the historic stroke of a pen, Governor Pritzker achieved something Democrats sought for years, placing a plan to change to a graduated income tax on the ballot.

“Voters will have the power to say yes to a fair tax system that will improve the trajectory of our state’s finances forever,” Pritzker said.

Since 1970, Illinois has had a flat rate income tax, currently 4.95%. Under Pritkzer’s so-called fair tax plan, that’s the top rate for anyone earning under $250,000.

But the rich get soaked, up to $500,000, 7.75%. Up to one million, 7.85%. And more than a million a year, 7.95%. Business groups claim, eventually, the middle class will pay more as well.

“Springfield politicians just can’t control themselves when it comes the opportunity of raising taxes. When you have the number and the governor that will sign it, they will do it,” said Greg Baise of Illinois Ideas.

“We had an old, antiquated, out-of-date tax code that didn’t work for an economy we actually had. It is not 1969,” said Toi Hutchinson (D-Olympia Fields.) “I don’t know who in here is still driving a 1969 car.”

A media war on the issue is expected to cost hundreds of millions in TV and direct mail, because the stakes are so high. To scrap the flat tax, 60% of Illinois voters, not just a simple majority, must approve the change.