The matchup between Democratic Gov. Pat Quinn and Republican businessman Bruce Rauner sets up a potentially historic campaign to the November election between two candidates each trying to convince middle-class voters he is their champion.
Quinn is a longtime populist politician famous for his youthful grass-roots efforts who more recently has trumpeted controversial Democratic-led causes like legalizing same-sex marriage and raising the minimum wage.
Rauner is a venture capitalist from Winnetka who has railed against "government union bosses" in his yearlong campaign for the GOP nomination and called lawmakers of both parties in Springfield "corrupt." Both won their parties' nominations for Illinois governor in Tuesday's primary.
Quinn won praise from public union backers by helping raise income taxes in 2011 when the state was facing its biggest deficit in history, but Illinois still has some of the worst finances in the country. And public employee unions made Quinn the enemy over cuts to their pension benefits.
Rauner touted his business experience as a credential as Illinois has an unemployment rate well above the national average, but he's presented few specifics to cure the state's ailing budget.
It's impossible to know what specific turns the likely aggressive, expensive campaign will take in the coming months.
But here are seven issues on which the two candidates likely will clash -- perhaps over and over again.
Lawmakers in Springfield crafting a state budget have assumed so far that the 2011 income tax increase will partly roll back on Jan. 1, but the next governor is set to take office days after that happens.
Rauner has proposed letting the tax expire as planned. And he opposes creating a graduated income tax in Illinois where people who make more money would pay a higher rate, saying it could raise taxes on middle class families.
Quinn argues the opposite, saying a graduated system would raise the taxes for the richest Illinoisans and even lower middle class taxes.
Changing Illinois' taxes would require changing the state constitution, and doing so doesn't require the governor to sign legislation. The change would be up to lawmakers and voters.
But not having a direct role in something has never stopped two politicians from making it a campaign issue.
Even though it has come at the expense of the public union members who often support Democrats, Quinn has touted the approval of controversial retirement benefit cuts for teachers and state workers.
Quinn has said he was "put on Earth" to deal with the state's $100 billion in pension debt, and he points to the cuts to argue he's working to get the state's ailing finances under control.
Still, Illinois remains behind on paying its bills, and lawmakers are looking to cut the state budget further this year, playing into Rauner's argument that Quinn and leading Democrats have botched Illinois' cash picture.
Rauner opposed the pension cuts, calling instead to move public workers' future retirement contributions into 401(k)-style plans. A behind-the-scenes, late-game push by Rauner last year almost killed the plan Quinn supported.
Rauner was stung by the issue in the primary campaign after he said at a campaign event he'd like to see the Illinois $8.25 per hour minimum wage lowered to the federal level of $7.25.
He later said he'd like to see the wage stay where it is, and could consider an increase if it came with a wide-ranging package of business reforms.
Quinn is all-in for a minimum wage hike, calling to raise it to more than $10 per hour.
Tuesday night, Quinn debuted a TV ad attacking Rauner over the issue, setting the tone for the coming months.
Quinn could seek to make the minimum wage an issue in part to draw attention to the personal wealth of Rauner, who made $53 million last year.
Rauner has sought a regular-guy image, though, airing a campaign ad in the primary to showcase an $18 watch he wears, often sporting a Carhartt jacket and riding a Harley-Davidson motorcycle to the Illinois State Fair this year.
Rauner's cash, though, helped him introduce himself to GOP primary voters via TV ads far better than his opponents. While Quinn is likely to get financial help from lots of sources in the campaign, he might not have the resources Rauner does.
Quinn took office in 2009 following the impeachment trial of the nearly universally maligned Rod Blagojevich, and the Democrat isn't likely to ever escape the fact that he was on the same ticket as the imprisoned governor twice.
In addition, Quinn has faced serious criticisms over a state audit that let his office distribute anti-violence grants in Chicago shortly before the November election.
Rauner faced criticism in the primary for some of the problems had by businesses his firm once invested in, and Quinn can be expected to bring those up again.
Rauner has said he would have vetoed the same-sex marriage legislation approved by lawmakers last year.
Quinn is the one who signed it.
In an election dominated by the economy, same-sex marriage could be a social issue voters look at.
Rauner supports the concealed carry law approved by lawmakers last year that allowed Illinoisans to carry hidden handgun in public for the first time.
Quinn vetoed that law in an effort to get further gun control measures approved, but lawmakers overrode him.