WASHINGTON -- People have been camping out for days in their ponchos and raincoats, hoping to get a front row seat to history.

On Tuesday, the U.S. Supreme Court begins two full days of examining same-sex marriage, looking at it from both the state and federal levels.

The first case is a challenge to California's 2008 ballot measure, known as Proposition 8. Voters approved the law, which defines marriage as between a man and a woman and effectively bans gay marriage.

The second looks at the Defense of Marriage Act, which only recognizes marriage as the union of one man and one woman under federal law.

The Supreme Court hearings are personal for Jessica Chipoco and Lindsey Dawson. They're getting legally married in Maryland this weekend, and they'd like Washington to recognize that marriage.

"We'd just be like on the same page as we are in the state that we live in if the federal government can extend that same right to us," Chipoco said.

Both women say they're hopeful.

"I just think it's incredibly moving," Dawson said. "I think it's a really exciting time personally because I'm excited to marry Jessica. But it's exciting in that you can feel the country shifting."

Meanwhile, the public is moving in their direction. Polls show most Americans now approve of same-sex marriage, with younger people supporting it and older people opposing it.

"So we see strong divisions among older Democrats and older Republicans," Dan Cox, with the Public Religion Research Institute, said. "But when we look at Millenials, that's Americans under the age of 30, we actually see the partisan differences diminishing."

Still, some conservatives like the Heritage Foundation's Ryan Anderson, co-author of the book What Is Marriage?, are trying to turn the tide.

Anderson filed a friend-of-the-court brief defending traditional marriage, arguing that marriage is already in crisis -- threatening society, kids, and the family unit.

"Same-sex attracted Americans are not to blame for the problem that we face in America right now," he told CBN News. "But the question we have to ask is do we want to double down on the mistakes of the last 40 years? Or do we want to start recovering a more sound understanding of what marriage is and why it matters?"

Anderson and others worry that legalizing same-sex marriage could have serious consequences.

For one, it could be the first step to redefining marriage altogether, possibly leading to polygamy or even group marriages with multiple partners. Some advocates of gay marriage openly support those ideas.

Also, same-sex marriage could eventually hurt religious freedom in America because churches, religious organizations, and even businesses will have to support whatever the government defines as a marriage or possibly face government action.

But Anderson believes there's hope for supporters of traditional marriage.

Just as the pro-life movement made its case for years and changed public opinion, leading to state laws limiting abortions, Anderson believes supporters of traditional marriage can do the same.

So as young people grow up, they will understand the value of the traditional family and change their views.

"Forty years later, my generation is now more pro-life than my parents' generation," Anderson said. "And the same thing is true for marriage. We're just starting this discussion about marriage."

These cases have the potential to settle the issue once and for all. While supporters of same-sex marriage hope they'll ultimately lead to equality and end the debate, opponents say whatever the rulings, they've only just begun in the fight to defend traditional marriage.

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