“We’d pay our bills,” Mr. Cullerton said. “Our vendors get paid. Our bond rating would improve.”

Republican leaders criticized the size of the proposed tax increase and complained that they had not been included in conversations where the plan was developed. Most of all, they argued that spending cuts needed to be looked at first, even given the urgency of the crisis, before anyone should resort to a giant and rushed tax hike.

The state’s Republican Party chairman, Pat Brady, on Saturday described the whole notion as “the latest example of life in Madiganville,” referring to the longtime speaker of the House, Michael J. Madigan, and introduced an online petition in which residents could urge lawmakers to thwart the tax increase.

On a recent afternoon, Tom Cross, the Republican leader of the House, said he believed that the situation in Illinois could be “catastrophic” as early as May or June, then ticked down a four-page list of proposals that he says Republicans have tried to offer as ways to truly sort out Illinois’s mess. On the list: sell half of the state’s fleet of cars, require only one license plate on cars instead of two, combine the state treasurer’s and comptroller’s jobs, ban out-of-state travel for elected officials, and end the remodeling of state offices (carpet included).

“Even if you have a tax increase like this, you can’t wake up and say, ‘I’ve got all the money in the world, and I can spend like a drunken sailor,’ ” Mr. Cross said. “This is all as bad as everyone says, and I still don’t hear any willingness to see the need to tighten the belt.”

Mr. Madigan, who is also the state’s Democratic Party chairman and, in the view of many, the state’s most powerful politician, has sent signals that more spending is not what he has in mind. He has pressed for two constitutional amendments  both of which Mr. Cross mocks as “gimmicks”  that would make it more difficult to approve benefit increases for pensioners and would hold state spending growth to a level residents see in their salaries.

As word of a possible deal filtered out, some in the business community were criticizing the size of the tax increases, saying they would make new companies less likely to come here and existing ones less likely to stay. Others were predicting that angry taxpayers might appear in droves in Springfield on Monday.