(CBS) — The six Democratic candidates for Illinois governor skirmished Tuesday during a fast-moving, televised forum, with billionaire JB Pritzker absorbing most of the blows but also launching a few of his own.

In their first chance to get free television exposure in a debate, both Chris Kennedy and Daniel Biss charged that nominating Pritzker would be playing directly into incumbent Gov. Bruce Rauner’s hands.

“The best thing for him in this election is to run against another billionaire who’s Mike Madigan’s candidate,” Biss said, referring to the Illinois House speaker whom Rauner has attacked politically.

“You hear him on those tapes, giving money to Blagojevich and then trying to get appointed to the treasurer’s job,” said Kennedy, a reference to Rauner attack ads against Pritzker that feature a wiretapped phone call between the Democrat and the disgraced former governor (Pritzker has not been accused of wrongdoing by authorities).

It was against Biss that Pritzker chose to return fire.

“You’re the only candidate on this stage that voted for Mike Madigan for Speaker of the House,” he said of Biss, a state lawmaker.

Biss countered: “He’s obviously concerned because he doesn’t want the Democratic primary voters of Illinois to face a choice between a middle-class progressive and a billionaire.”

All but one candidate, Robert Marshall, backed a progressive income tax, and all endorsed legalizing recreational marijuana in Illinois.

But when each candidate was asked to point out one accomplishment by an opponent, only Kennedy was stumped.

“When JB emerges as the poster child of all that’s wrong with the corrupt system in our state, it’s difficult for me to heap praise on him,” he said.

After the debate, Kennedy said he apologized to Pritzker and praised him for his work in early childhood education.

Also running for the Democratic nomination are community activist Tio Hardiman and regional superintendent Bob Daiber.

Rauner, a Republican, seeks a second term in office. He faces a primary challenge from state Rep. Jeanne Ives.