Nathan Collier with his wives Victoria and Christine. (via KRTV News)

Opponents of same-sex marriage have commonly invoked the "slippery slope" argument for why it shouldn't be legalized. Once you let gay people marry, the argument goes, it could open the door to things like polygamy — or even bestiality.

Well, no one's married their dog since the Supreme Court's ruling last week, but in Montana, polygamists Nathan, Victoria and Christine Collier — inspired by the same-sex marriage victory — applied for a marriage license Tuesday. Nathan Collier said he plans to sue if it's denied and told the Associated Press: "It's about marriage equality. You can't have this without polygamy."

But while support for polygamy is rising, it has a ways to go before it catches up with same-sex marriage, and there are plenty of reasons it's unlikely to catch on in anywhere near the same way.

For now, it's illegal nationwide, recent legal attempt to overturn bans have been unsuccessful, and public support is low. But that support is increasing.

According to data from Gallup, support has increased from 5 percent in 2006 to 16 percent today. The biggest one-year jump happened in 2011, after TLC's "Sister Wives," about a polygamist family who lived in Utah and later Nevada (the Colliers also have appeared on the show), first aired.

(The Washington Post)

Some polygamists have become champions of same-sex marriage because they see it as as opening for them, even if it often goes against their personal religious beliefs. They've also taken cues from how opinions about same-sex marriage evolved. Getting on TV and showing people how normal you are is an important component of that.

Much has been made about the role entertainment played in shaping public opinion on LGBT issues. When Vice President Biden came out in support of same-sex marriage in 2012 on "Meet the Press," he said the television show "Will & Grace" "probably did more to educate the American public than almost anything else." There's an argument to make that "Sister Wives" has done the same for polygamists. Before the show aired, much of what the public knew, saw and read about polygamy was about Warren Jeffs, the polygamist leader arrested in 2006 and accused of raping teenage girls, and his wives, who wore unusually long hair, prairie dresses and lived in compounds. No wonder support was so low in the late '00s.

But "Sister Wives" presented a family that lived in the suburbs, sent their kids to public school and wore blue jeans. The idea of who polygamists were, at least among those who watch TLC, evolved from pedophile rapists in cults to consenting adults who agreed to live in families with one husband and multiple wives but were otherwise pretty average. If you can couple that with a libertarian argument for decriminalizing polygamy that appeals to the growing number of Americans who support issues like same-sex marriage and marijuana, it seems like a winning blueprint for changing public opinion. At least somewhat.

But polygamists will always be at a disadvantage compared to the LGBT community. The No. 1 reason people who once opposed same-sex marriage changed their mind, according to a 2013 Pew poll, was that they knew someone who was gay or lesbian. Unlike sexual orientation, polygamy isn't something most people will ever confront in their daily lives, nor is thought of as a trait someone is born with.

The communities that polygamists typically come from — including the Browns and the Colliers — are Western, Mormon and not very sympathetic. It's not as if people are coming out as polygamists across the country and are changing their friends' and families' minds. Although some Mormons practiced polygamy in the 19th century, the Church of Jesus Christ of Latter-day Saints is aggressively anti-polygamy today. It banned the practice in 1890, and members found practicing it are excommunicated.

In fact, there's evidence to suggest that coming out as gay to your Mormon parents is more acceptable than coming out as polygamist. A September poll found that 48 percent of Utahns opposed same-sex marriage, while a 2013 poll found 61 percent of Utahns believe polygamy is morally wrong. (Granted, not all Utahns are Mormon and not all Mormons are Utahn, but in lieu of polling data on Mormons specifically, looking at the state where six out of 10 residents are is the closest thing we have).

So while polygamists might see the same-sex marriage ruling as a victory for them, there's no guarantee courts will feel the same way. And for now, neither will a majority of Americans.