Lipinski is the only House Democrat not to co-sponsor the Equality Act, which is expected to hit the floor later this week for a vote. That had drawn criticism from his primary challenger, Marie Newman, who is seeking a rematch after narrowly losing to Lipinski last year by 2 points.

ADVERTISEMENT In a speech on the House floor on Wednesday, Lipinski said that he would vote for the bill but wants religious liberty concerns to be addressed before it becomes law.

"All Americans deserve equal treatment under the law and should have these rights protected, including individuals in the LGBT community," Lipinski said. "At the same time, the free exercise of religious belief is a core ideal of our country, protected in the Constitution and through federal law."

"It is critical to ensure that religious freedom stands a chance to be fully lived out and fairly treated in court. This week, I will vote for the Equality Act for the broader goal. But before it becomes law, we must do more to ensure religious liberty," Lipinski added.

After House Democrats introduced the legislation in March, Newman sent a fundraising email highlighting Lipinski's lack of support.

"There’s one House Democrat — one in the whole country — who doesn’t support this civil rights legislation: Dan Lipinski," Newman wrote in the email. "Once again, he’s bucking the Democratic Party to stand against equality, something he’s done consistently throughout his 14 years in Congress."

Newman has secured support from multiple progressive groups, including MoveOn, Democracy for America and the Progressive Change Campaign Committee.

GLAAD, an LGBT advocacy group, recently launched a digital campaign calling on Illinoisans to pressure Lipinski to support the bill.

"Congressman Dan Lipinski’s concerns about the balance between religion and government are a false flag. Religion is an American value that’s treasured in this country – including for the LGBTQ community – and is not compromised in any way by ensuring equal rights and dignity for all people," Zeke Stokes, GLAAD chief programs officer, said in a statement.

Newman has sought to run to Lipinski's left on a variety of social issues, including abortion and gay rights.

Lipinski told the Chicago Sun-Times last year that he supports same-sex marriage "because it has been declared the law of the land," but added that "personally, I don’t support it, but that doesn’t matter in how I vote."

Lipinski also co-sponsored the First Amendment Defense Act, which would prevent the federal government from taking adverse action against people based on their beliefs about marriage. Gay rights activists argue the measure is designed to effectively allow discrimination against same-sex couples.

But Lipinski said he supported the bill out of concern that churches could lose their tax-exempt status.