J.B. Pritzker is a member of the billionaire Pritzker family, best known for owning the Hyatt hotel chain. After months of speculation, Pritzker announced in April 2017 that he would enter the race to unseat Gov. Bruce Rauner.
A powerful Democratic fundraiser, Pritzker was deeply involved in both of Hillary Clinton's presidential campaigns and has contributed to candidates including Chicago Mayor Rahm Emanuel, as well as Senators Dick Durbin and Tammy Duckworth. His sister Penny Pritzker served in President Obama's administration, while Pritzker himself unsuccessfully ran for Congress in 1998.
A venture capitalist, Forbes listed Pritzker as the 219th richest person in the country in 2017, with a net worth of $3.4 billion - making him capable of self-funding his campaign, even more so than Rauner. As of September, Pritzker has given his campaign more than $126.5 million.
That cash bought him a massive field operation and hours of advertising airtime ahead of the March primary, inundating television airwaves to tout his endorsements and his vow to "stand up" to President Donald Trump and Rauner - a strategy that lifted him to victory with 45 percent of the vote against five other candidates in the Democratic primary.
Having never held elective office, Pritzker doesn't have a legislative record but has said he supports raising the minimum wage to $15 an hour, has proposed the introduction of a public health insurance option, and is in favor of legalizing marijuana.
He has not released a detailed tax plan but has said he supports changing Illinois' income tax rate from a flat tax to a graduated, or progressive, income tax which would tax wealthier individuals at a higher rate.
To do that, voters would have to approve a change to the Illinois Constitution, which is a tall order in itself. If enacted, the policy - proven to be politically treacherous at times - could take years to implement, if at all. Pritzker has not revealed details on how he would go about changing Illinois' tax structure.
Both Rauner and Pritzker's opponents in the Democratic primary have hit Pritzker - a longtime political donor and power player behind the scenes - on his ties to the so-called "machine," particularly House Speaker Michael Madigan.
Rauner has also taken aim at Pritzker over leaked tapes, recorded by the FBI in a 2008 wiretap, in which the Democratic candidate can be heard discussing political appointments for himself with now-incarcerated Gov. Rod Blagojevich, as well as making off-color comments about black politicians to potentially replace newly-elected President Barack Obama in the U.S. Senate.
That controversy didn't appear to outwardly impact Pritzker's relationship with Obama, as the former president offered his endorsement of the gubernatorial candidate in August.