Opponents of a proposed gay marriage bill in Illinois are set to demonstrate Saturday outside the office of Illinois State Representative Linda Chapa LaVia.

Chapa LaVia, a Democrat, voted against a 2010 bill legalizing civil unions for gay and lesbian couples in the state. However, supporters of marriage equality put her in the undecided category on marriage.

The bill, which seeks to make Illinois the 10th state to legalize such unions, awaits a vote in the House after passage in the Senate.

Demonstrators from the Illinois Family Institute are set to protest outside Chapa LaVia's office in Aurora, Illinois' second most populous city after Chicago.

The group staged a similar protest last weekend against Rep. Ed Sullivan, the second House Republican to announce support for the measure. About 150 demonstrators gathered in front of Sullivan's district office in Mundelein. Protesters carried signs which read “Don't Change What God Ordained” and “Same-Sex Marriage Harms Religious Freedom.”

A counter protest is being organized by Illinois Unites for Marriage, the coalition of groups lobbying for passage of the measure.

“It's absolutely critical that we show Representative Chapa LaVia just much support there is for the freedom to marry,” the Human Rights Campaign (HRC), a coalition member, said in a blog post.