Headed by former Republican National Committee Chairman Ken Mehlman, over 300 members of the Republican Party who have served in politics filed an amicus brief on Thursday to sway the Supreme Court to support same-sex marriage. The Court is scheduled to consider four same-sex marriage cases on April 28 that could make it legal across the nation.

Mehlman has been an ardent proponent of same-sex marriage; in 2013, he headed a group that helped reverse California’s Proposition 8, which was approved by the state’s voters and banned same-sex marriage in the state.

Twenty-three current and former members of the House of Representatives and Senate and seven current and former governors have endorsed the brief, including Sens. Susan Collins and Mark Kirk, Massachusetts Gov. Charlie Baker, and former Utah Gov. Jon Huntsman. Former New York City Mayor Rudy Giuliani, retired Gen. Stanley McChrystal, and billionaire GOP mega-donor David Koch have also joined the effort.

Many of Mitt Romney’s top aides from his 2012 campaign, including his general counsel, also signed the brief, which originated in 2013.

Mehlman told TIME, “There’s been an increase since the last time in public support for marriage equality across all ideological, racial, and political groups.”

The brief itself is attempting to tear down the bans on same-sex marriage in Kentucky, Michigan, Ohio, and Tennessee. It states that the bans are “inconsistent with amici’s understanding of the properly limited role of government.” It goes on to indicate:

Although amici hold a broad spectrum of socially and politically conservative, moderate, and libertarian views, amici share the view that laws that bar same-sex couples from the institution of civil marriage, with all its attendant profoundly important rights and responsibilities, are inconsistent with the United States Constitution’s dual promises of equal protection and due process.

Last October, the Court refused to consider the challenges to appellate court rulings that five state same-sex marriage bans were unconstitutional. There has been scuttlebutt that some 2016 potential GOP presidential candidates want the court to approve of same-sex marriage so it will not be a political issue for them in 2016.

After the SCOTUS decision last October, Faith and Freedom Coalition’s Ralph Reed, wary of GOP candidates running away from the issue, warned, “For candidates running in 2014 and those who run for president in 2016, there will be no avoiding this issue.”

Wisconsin Gov. Scott Walker, who opposes same-sex marriage, said last October, “The federal courts have ruled that this decision by this court of appeals decision is the law of the land and we will be upholding it.”

New Jersey Gov. Chris Christie, also personally opposed, had already said the issue was “settled” in New Jersey last summer.

Louisiana Gov. Bobby Jindal, another opponent of the practice, added after the SCOTUS decision in October, “The law is certainly in the Court’s court.”

Former Florida Gov. Jeb Bush said after Florida adopted same-sex marriage in January:

I hope that we can show respect for the good people on all sides of the gay and lesbian marriage issue — including couples making lifetime commitments to each other who are seeking greater legal protections and those of us who believe marriage is a sacrament and want to safeguard religious liberty.

Mehlman was seemingly unfazed by conservative opposition to same-sex marriage, stating, “Republicans traditionally have great respect for court decisions, particularly the Supreme Court,” adding, “The data shows that public acceptance increases very quickly, and very significantly.”