SPRINGFIELD — With an early May deadline looming, several proposals to amend the Illinois Constitution are advancing in the General Assembly.

The Senate Executive Committee voted Tuesday to send three proposed amendments to the full Senate for a vote, and House committees did likewise Monday with two measures.

It's ultimately up to voters to decide whether to change the state Constitution. If the Legislature wants to put a question to voters, each chamber must approve the proposal by a three-fifths majority at least six months before the next general election. Lawmakers are limited to asking voters to change three articles of the Constitution in a given election, which means not all of the proposals heading to the chamber floors can end up on the November ballot.

The Senate committee approved measures that would do away with the Constitution's flat tax provision, change the way legislative and congressional districts are drawn and eliminate the lieutenant governor's office.

House committees approved a different redistricting plan and a proposal from House Speaker Michael Madigan, D-Chicago, that would require the state to cover the majority of the cost of public education.

Sen. Don Harmon, D-Oak Park, chairman of the Executive Committee, is sponsoring the amendment that would allow Illinois to begin charging different tax rates based on income.

Harmon said the proposal "would allow Illinois to join the modern era" and noted that neighboring Wisconsin has a graduated income tax system.

The proposal is accompanied by a bill that would lower the tax rate for 99 percent of taxpayers while raising rates for wealthier residents on their income above certain thresholds. For example, an unmarried person would pay 8.75 percent on income between $500,000 and $1 million and 9.75 percent on income more than $1 million. The current rate is 3.75 percent for all taxpayers.

The proposed amendment itself doesn't deal with what the rates would be, one of many concerns the idea raised for Republicans. Sen. Sue Rezin, R-Morris, called it "an open door for allowing higher taxes on the middle class."

An identical proposed amendment, sponsored by Rep. Christian Mitchell, D-Chicago, is scheduled for a House committee hearing Thursday.

The Senate redistricting plan, sponsored by Sen. Kwame Raoul, D-Chicago, is substantially different from one being considered in the House and one being pushed by a group called Independent Maps.

Unlike those proposals, which would create independent commissions, Raoul's plan would leave the process for drawing district lines in the hands of the General Assembly, with approval from the governor.

It would do away with the current system of dividing each state Senate district into two state House districts, making the boundaries independent. This would enable better representation of minority communities, Raoul said.

Sen. Tom Cullerton, D-Villa Park, is proposing the elimination of the lieutenant governor's office, a move he says would show the state's commitment to consolidating government operations and save $1.6 million annually, a minute fraction of the state's roughly $36 billion budget.

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While his fellow Democrats passed the bill out of committee, most indicated that they wouldn't support it on the Senate floor.

One of their concerns is that the change would set up a situation in which a vacancy in the office of governor could be filled by an attorney general — the next official in the line of succession — of a different party.

Cullerton noted that his proposal is identical to one sponsored by U.S. Rep. Darin LaHood, R-Peoria, when he was in the state Senate. Despite that history, it failed to win any Republican support.

A House committee last week approved a similar proposal.

Also in the House, Madigan's proposed education funding amendment is headed for a floor vote.

The speaker, who was a delegate to Illinois' 1970 constitutional convention, said the measure is intended to enshrine that education is a "fundamental right" and one that should be primarily the state's obligation to fund.

The measure wouldn't set up a specific formula for funding schools. That would be up to the Legislature to determine based on the new requirement if it's approved by voters, Madigan said.