As the Supreme Court weighs the constitutionality of California's Proposition 8 ban on same-sex marriage, advocates on both sides of the issue are looking to the justices' ruling to determine whether the issue remains at the forefront of political and cultural debate — particularly within the Republican Party.

If the court rules to overturn Proposition 8, conservative opponents of same-sex marriage argue that the issue will move to the center of Republican political discourse, in much the same way that Roe vs. Wade and abortion became the party's defining wedge issue in the 1980s and '90s.

"It strikes me that what we have right now is exactly what the genius of our federal system was designed to provide — a broad range of local solutions and arrangements to what is a contentious issue," said evangelical operative Ralph Reed, who leads the Faith and Freedom Coalition.

"If the court were to go to the most extreme case and strike down 41 state laws defining marriage as between a man and a woman by an act of judicial fiat, I think it will further polarize our politics, it will undermine the legitimacy of the Supreme Court, and it will likely spark a marriage equivalent of the pro-life movement that will spend decades trying to reverse the decision," Reed said.

A national debate about gay marriage would be the worst-case scenario for the Republican Party as it moves to sideline social issues in an attempt to broaden its appeal to a wider swath of voters.

The problem for the GOP is borne out in recent polling. A Pew poll released last week found that while support for gay marriage is growing among the general public — 48 percent of Americans now approve of gay marriage, up from 38 percent in 2003 — white evangelicals remain staunchly opposed, with only 19 percent expressing support for gay marriage. The divide is also apparent among younger evangelicals, with 65 percent of those under 25 opposed to gay marriage and 30 percent supporting it.

Nowhere is this issue more salient for the GOP than in Iowa, a key early voting state where conservative white evangelicals play a major role in determining the Republican presidential nominee.

"If you're running for president in 2016 and you don't want to have to talk about these issues, you're certainly going to hope that the Supreme Court doesn't overextend its jurisdiction," said Steve Deace, an influential conservative Iowa talk radio host. "Because if it does, you're going to see an entire presidential primary defined by this issue."

"This idea that some people have that the court is going to settle the issue in the Republican Party — it's going to do the exact opposite," Deace added. "It's going to raise the issue to Orange Threat Level, it'll be DEFCON 6…It will become the defining litmus test."

"All these pro-family groups, all of these people have invested decades in this fight, they've invested lots of human resources and human capital, they are not all going to throw up their hands," Deace said. "They're going to double down, it's going to be even nastier, it will be an even more defined issue."

Regardless of how the court decides on Proposition 8, however, conservatives say that the issue is likely to continue to divide the GOP, pitting social conservatives against the party's more moderate Establishment leaders.

"On a national level if the issue fades away for the Republican Party, they are going to lose tons of conservatives," said Matt Floyd, an Iowa pastor who leads the lobbying group Conservative Christians for America. "I think it will galvanize conservatives and you'll see them link up."

Iowa Republican Party Chair A.J. Spiker highlighted these concerns in a recent letter to Republican National Committee leaders obtained by Business Insider.

"While inclusion is important, elected Republicans (we all know the most recent example) and National/State Party leaders who embrace so-called same sex marriage are doing grave harm to our Party and the whole of society," Spiker wrote, apparently referencing Ohio Republican Sen. Rob Portman, who recently came out in support of gay marriage.

"Lets not forget, so-called same sex marriage is an irreconcilable difference with the Republican Party's largest constituency... Committed Christians."