CHICAGO — Expect a decision no later than Thursday on the citizen initiative to create an independent commission to draw Illinois legislative districts rather than let politicians do it.

Every 10 years Illinois’ politicians, directed by party leaders, draw political maps based on U.S. census data. Critics say that’s politicians picking voters instead of voters picking their elected officials.

Nearly 600,000 citizens signed a petition to place a measure on the November ballot to change the system. The proposed constitutional amendment is being challenged in the courts by a group linked to longtime House Speaker and Democratic Party boss Michael Madigan.

Independent Map Coalition Campaign Manager Dave Mallet said Thursday is the latest the Cook County judge said she would issue a ruling.

Mallet said the objectors are in the minority.

“It’s a very important power for party leaders and for legislative leaders to have, and they don’t want to give that up, and that’s why there are people opposing this,” he said. “On the other hand, there’s 60 percent of voters in Illinois who have already said they’ll support this.”

Mallet said Independent Map attorneys took notes from a previous failed attempt and are confident they’ll prevail. This week’s ruling, however, probably won’t be the last. Regardless of the ruling, the case is expected to go all the way to the state Supreme Court.

“People have always sued to prevent the voters from changing the Constitution on their own, and it often is decided by the Illinois State Supreme Court, so they just so happen to be the final level of appeal for one side or the other,” he said.

Mallet said Aug. 26 is the deadline to certify the measure for the November ballot.