AILSA CHANG, HOST:

Now a primer on the election for governor in Illinois. Tomorrow is the primary. Both Democrats and Republicans will consider men with vast personal fortunes and significant political baggage. From the statehouse in Springfield, Illinois Public Radio's Brian Mackey reports.

BRIAN MACKEY, BYLINE: The first thing you need to know is that Governor Bruce Rauner is unpopular - like, deeply unpopular. Just three years into his first term, his approval rating is 31 percent, among the worst in America. That's partly because he presided over a two-year budget standoff that only ended when some of his fellow Republicans turned on him, working with Democrats to raise taxes. Then Rauner outraged conservatives by signing a pair of Democratic bills dealing with immigration and abortion.

All this has set off a fierce competition among Democrats who see an opportunity to take back a blue-state executive mansion. But we'll come back to that in a bit. First, like Rauner, we have to get through the Republican primary.

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JEANNE IVES: He's betrayed our party. And you know what? You cannot buy back trust after betrayal.

MACKEY: This is Jeanne Ives. She's a state representative who's giving Rauner an unexpected run for his money. Rauner has tried to pretend he doesn't notice her campaign.

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BRUCE RAUNER: It's part of the process. You get some fringe elements or whatever coming in as part of a campaign. And these things happen.

MACKEY: That's what Rauner says. His actions, however, reveal he's taking her insurgency more seriously. He's refused to debate her and is spending money on attack ads - not that he's feeling pinched. One of the other important things to know about Rauner is that he has a lot of money - hundreds of millions of dollars made during a career as a private equity investor. That means, assuming he can fend off Ives' longshot primary challenge, Rauner will have an essentially limitless supply of cash with which to compete for a second term.

So how are Democrats going to deal with that? It's led to the question animating their primary. Namely, do Democrats need their own billionaire? Enter Jay Robert Pritzker, who goes by the initials J.B. He's one of the heirs to the Hyatt hotel fortune, which makes him a billionaire several times over. Pritzker has completely self-funded his campaign, in the process shattering state records. And he's promising Democrats he'll share the wealth.

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J B PRITZKER: It isn't just about beating Bruce Rauner. It's about electing every Democrat everywhere in this state.

MACKEY: His main rivals for the nomination are Daniel Biss, a state senator with a Ph.D. in math from MIT, and Chris Kennedy - yes, one of the Kennedys - among Bobby and Ethel's 11 children. Both men have been competing to be the main alternative to Pritzker, whose wealth has allowed him to dominate the airwaves for the better part of a year, putting him ahead in polling. But Pritzker has his own liabilities.

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ROD BLAGOJEVICH: You don't want to be secretary of state, do you, J.B.?

PRITZKER: Oh, I wasn't pushing for me...

BLAGOJEVICH: Yeah.

PRITZKER: ...To be secretary of state. I mean...

MACKEY: This is an FBI wiretap of Pritzker chatting with then-Governor Rod Blagojevich. You might remember him as the guy who went to prison for trying to sell Barack Obama's Senate seat. Now, Pritzker was never accused of wrongdoing, and these tapes were never played at trial. But the Chicago Tribune obtained them. And in discussing potential Obama successors, Pritzker did make racially insensitive remarks.

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PRITZKER: You know, but if you're forced to put an African-American in the spot, the one, you know - the least offensive and maybe get to the most is Jesse White.

MACKEY: The least offensive African-American Jesse White is Illinois's popular five-term secretary of state. And he forgave Pritzker. But the fundamental question for Democrats remains. When facing a Republican with essentially limitless wealth, are Pritzker's billions worth the baggage in which they're packed? Voters have until tomorrow evening to decide. For NPR News, I'm Brian Mackey in Springfield, Ill.

(SOUNDBITE OF SLIM'S "AMSTERDAM BLUES") Transcript provided by NPR, Copyright NPR.