Gov. Bruce Rauner touted the historic education bill as his “biggest accomplishment” last year, but on Tuesday Democratic challenger J.B. Pritzker vowed to kill one of its key components — a private school scholarship tax credit that Pritzker dubbed “a back-door school voucher program” and “a really bad idea.”

The Chicago Democrat said the Republican governor deserves no credit for the rest of the bill, since he’d vetoed it twice.

“Last year Bruce Rauner forced a school funding crisis on Illinois,” Pritzker said. “He vetoed critical school funding legislation, stuck a back-door school voucher program onto the bill. And then he vetoed yet another school funding bill. Rauner has taken every opportunity to jeopardize funding for our schools, destabilizing our education system and creating division in our state.”

Speaking at the Harold Washington Library on Tuesday — two weeks after he handily won the Democratic primary — Pritzker rolled out his own vague plan to get the state on better financial footing: a progressive income tax that could take up to two years to get going and would require a constitutional amendment.

Rauner’s campaign, in turn, seized on the blurry plan as proof that their Democratic rival would raise taxes should he win. Pritzker favors a progressive income tax, in which higher earners would get taxed at a higher rate. The state currently has a flat tax where all residents are taxed at the same rate. And Rauner is pushing for a rollback of the income tax, which went up last year when the state finally ended a budget impasse.

Pritzker touted a progressive income tax “to protect the middle class and those striving to get there; that allows us to provide adequate education funding and to lower property taxes across Illinois.”

The Democrat also took aim at the new program Rauner pushed that lets donors to private school scholarships take $75 million in tax credits.

Pritzker told reporters he’d get rid of the program “immediately” should he win in November: “We’re going to get rid of them. I think diverting money away from public schools right now to private tuition tax credits seems like a really bad idea. We need to make sure we’re funding our public schools before we start talking about anything.”

Pritzker admitted his own funding source, a progressive income tax, would take “a little time” — about two years — to get passed by the Legislature. He said he’d want a Massachusetts model in the meantime, “an artificial progressive income tax, in which we would raise the exemptions for those striving to get to the middle class … and raise the overall rate and the raise the earned income tax credit at the same time. All of which would create a kind of artificial gradual income tax in the state.”

But when asked for specifics about the graduated income tax — and how much the rate would be — Pritzker offered none.

“Well, again, just like with the constitutional amendment, really you’d have to negotiate with the Legislature over what those rates are and look at the budget for that year that you’re putting it in placed for,” Pritzker said. “So you really couldn’t name the rates until you have that negotiating process.”

As for the amount of revenue he’d want to generate, Pritzker said he’d work to legalize marijuana to get half a billion to $750 million in new revenue dollars, and he’d work to try to increase education funding by $350 million a year.

Pritzker, the billionaire entrepreneur and philanthropist, won the Democratic primary on March 20, and since then has shifted his focus to a #RaunerFailedMe series, trying to show voters ways he believes the embattled governor failed the state.

On Tuesday he brought the series to the downtown library, where the Pritzker family name was highlighted throughout the historic library. The Cindy Pritzker Auditorium in the library’s basement is named after Pritzker’s aunt.

Pritzker said Rauner’s biggest claim of success — the historic education funding bill last year — is actually another example of failed leadership.

Gov. Bruce Rauner gives a student a high five after signing an education funding reform bill at Ebinger Elementary School on Aug. 31, 2017. File Photo. | Ashlee Rezin/Sun-Times

“Well, if you veto it twice, I’m not sure how you get credit for it. The truth is that it was [State Sen.] Andy Manar’s bill. It was Andy Manar who fought for this for six years, and it was over the objection of Rauner and the Republicans who voted against it, that they actually got the thing passed,” Pritzker said. “I’m not sure once again how the governor can claim any credit for it. To me when you put commercials on like he did, claiming credit for something you veto, and that you held hostage for so many months, it seems to me that you don’t get to take credit.”

Last December, Rauner’s campaign released a list of top 10 accomplishments for the year, with “historic education funding reform” at the top of the list.

“Thanks to Governor Rauner’s influence, this bill distributes funding more equitably across the state and puts in place a school choice program to provide low-income families with greater education options for their children,” the Rauner campaign said.

While Rauner took credit for the bill, he took heat in August because he vetoed a version the House and Senate had agreed to after lengthy negotiations. The governor had even called the initial Democratic-sponsored bill a “Chicago bailout.”

The bill Rauner signed into law in September ended up giving CPS even more money.

On Tuesday, Rauner’s campaign said the governor “was proud to sign the education reform bill.”

“He vetoed initial versions in order to negotiate a better final product — which he successfully accomplished by creating the tuition scholarship tax credit program to benefit low-income students,” spokesman Will Allison said in an email.

Allison called it “shameful” that Pritzker would end the program, which he said will enable low-income students to get a “better education.”

“It’s clear Pritzker is out-of-touch with struggling families who can finally choose a brighter future for their children,” Allison said.