A poll of Illinois residents has found that half of people living in the state supported a bill to legalise equal marriage, with the percentage in opposition to it much lower.

The Ipsos poll, comissioned by Crains, of 600 adults in the state last week, showed that 50% supported the Religious Freedom and Marriage Fairness Act, which would legalise equal marriage.

In opposition to the bill were 29%, meaning that over 20% had no opinion on the bill, and no uncertain feelings.

Crains wrote: “As expected, support is strongest in Chicago, with 56 percent backing passage. A majority of 52 percent of suburban residents supports approval, but support drops to a plurality of 48 percent downstate.

“The online survey had an accuracy rate of plus or minus 4.7 percent statewide, with wider ranges for numbers specific to Chicago or its suburbs.”

The study also suggested that those in support of equal marriage felt more strongly about the issue. out of the 50% supporting equal marriage, 37% do so “strongly”, 13% do “somewhat.

In opposition to equal marriage, out of the 29%, 19% “strongly” oppose, and 10% “somewhat.

Strong constituent support for the bill doesn’t necessarily mean it will be passed by lawmakers.

Last week, the Illinois Senate approved a bill to legalise same-sex marriage – although it still has to pass the House before it becomes law.

On Thursday – Valentine’s Day - the Senate, which is controlled by the Democrats, voted 34-21 to approve the measure.

However, House Republican Leader Tom Cross said he was not sure whether it would gain Republican support.

Earlier this month, the bill passed the Illinois Senate Executive Committee.

The Senate attached an amendment before passing the legislation which states no church or religious organisation would be forced to perform same-sex marriages.