They want to boost the personal income tax rate temporarily by up to 75 percent, pushing the current rate of 3 percent as high as 5.25 percent.
In sheer percentage terms, the Illinois proposal could be the biggest tax increase that any state has passed while grappling with recent economic woes.
The move is both difficult and bold. Democrats have only until noon Wednesday before losing some lame-duck lawmakers and a slice of their majority when a new General Assembly begins.
Republicans reject the tax proposal completely, while rank-and-file Democrats are pushing back. Some want strict new spending limits and others want a smaller increase.