As the state Senate returned to the Capitol Wednesday to begin its weeklong lame-duck session, both sides of anticipated gay marriage legislation were winding up for a fight.
A day after Cardinal Francis George urged parishioners to fight a bill that would allow gay marriage in Illinois, supporters of the bill said they have enough votes to make the state the 10th to legalize same-sex unions.
Cardinal George said that if lawmakers allow gay marriage in Illinois, they will be "acting against the common good of society."
"The state has no power to create something that nature itself tells us is impossible," Cardinal George wrote in a letter.
The Religious Freedom and Marriage Fairness Act could be introduced by Rep. Greg Harris and Sen. Heather Steans this week when the legislature reconvenes. New lawmakers will be sworn in Jan. 9.
Both Mayor Rahm Emanuel and Gov. Pat Quinn have expressed their support of a same-sex marriage bill, and in the days before Christmas, more than 200 rabbis and pastors issued a joint letter urging lawmakers to pass the bill. President Barack Obama also reportedly urged lawmakers to support same-sex marriage.
Bishop James Alan Wilkowski, of the Evangelical Catholic Diocese of the Northwest, voiced his support of the bill in a letter Wednesday saying the arguments of the Catholic Church "lack the foundation for the statewide conversation we are currently in."
"We believe that the institution of marriage will be strengthen for ALL married couples through the inclusion of gender-common couples," Bishop Wilkowski wrote.
Not everyone agrees.
David E. Smith, executive director of the Illinois Family Institute, told Ward Room the legislature should strike down the bill. "They don't have the right to go around and demand that we redefine a historical institution that has been understood for thousands of years as the union of one man and one woman," Smith said.
Members of Illinois religious groups -- from Catholic to Muslim -- on Wednesday sent every state lawmaker a letter calling gay marriage "dangerous'' to religious freedom.
The letter was signed or supported by leaders of more than 1,700 churches, congregations and faith groups.
Harris and Steans say public opinion favoring equal rights for same-sex partners is moving rapidly. Constituents in four states voted in favor of the issue or opposed a ban on it during the November election.
Harris successfully brought civil unions to Illinois in June 2011. He and Steans say a gay marriage law wouldn't interfere with religious beliefs or force places of worship to recognize same-sex marriages.
The Associated Press contributed to this report.