A coalition of 83 conservative groups sent a letter to Senate Minority Leader Mitch McConnell (R-KY) on Tuesday urging him to block the Respect for Marriage Act.

“H.R. 8404 would require federal recognition of any one state’s definition of marriage without any parameters whatsoever. This would include plural marriages, time-bound marriages, open marriages, marriages involving a minor or relative, platonic marriages, or any other new marriage definition that a state chooses to adopt, including through undemocratic imposition by a state Supreme Court,” the group, led by the Alliance Defending Freedom, claims.

“We call on you to reject H.R. 8404 and to urge your colleagues to thoroughly abandon this harmful and unnecessary legislation,” the letter, signed by Family Research Council president Tony Perkins, Focus on the Family president Jim Daly, and others, concludes.

In a separate letter, the Conservative Action Project claims that the Supreme Court’s decision in Obergefell v. Hodges, the 2015 case that established the constitutional right to same-sex marriage in the U.S., “unleashed religious freedom violations across the land, launching a new era of harassment and coercion of millions of Americans who hold a sincere religious belief or moral conviction that marriage is, or ought to be, between one man and one woman.”

McConnell has yet to take a stance on the Respect for Marriage Act, which House Democrats passed last week with the support of 47 Republicans. The bill is intended to enshrine the right to same-sex as well as interracial marriage into law following the Supreme Court’s decision striking down Roe v. Wade and Justice Clarence Thomas’s call for the court to reconsider Obergefell v. Hodges.

Senate Democrats need to pick up 10 Republican votes in order to pass the law, and several key GOP lawmakers have signaled their support for the bill. Sens. Susan Collins (R-ME) and Rob Portman (R-OH) have said they will vote for it, while Sens. Thom Tillis (R-NC), Lisa Murkowski (R-AK), and Ron Johnson (R-WI) have all signaled that they will likely vote for the bill. Along with McConnell, Sen. Mitt Romney (R-UT) hasn’t said whether or not he will vote for it.

The letters to McConnell are aimed at countering efforts on the part of progressive and LGBTQ organizations to sway Republican senators.

Proponents of the legislation are hopeful that they stand a chance of securing 10 Republican votes, due in part to the strong support for marriage equality across party lines. According to a 2022 Gallup poll, 71% of Americans support the right to same-sex marriage. A 2021 poll found that 55% of Republicans are in favor of marriage equality.