As Americans become more liberal, will Supreme Court follow on gay marriage?

The US Supreme Court isn’t supposed to be driven by public opinion, certainly not by political polls.

But if today’s Supreme Court justices – soon to make what will undoubtedly be a landmark decision on same-sex marriage – were to pay attention to public opinion, they’d see an America that is steadily and quite rapidly moving left to support gay rights, including marriage.

A string of four Gallup polls this past week bears this out. The bottom line: record numbers of Americans support gay marriage; say sexual orientation is something individuals are born with rather than something that is determined by upbringing or environment; and are now just as likely to consider themselves liberal as they are to self-identify as conservative.

• Sixty percent of Americans now support same-sex marriage, up from 55 percent last year and the highest Gallup has found on the question since it was first asked in 1996.

“Support for the legality of gay marriages in the US has been a fast-changing trend,” Gallup reports. “Just two decades ago, only 27 percent of Americans backed gay marriage, while 68 percent opposed. By 2005, the percentage in favor had increased by 10 points to 37 percent, and by 2010 it had reached 44 percent.”

Although Democrats and Independents are more likely to support same-sex marriage (76 percent and 64 percent, respectively), the number of Republicans supporting such marriages has more than doubled over the past five years to 37 percent. The difference between the two parties is tied to the age of party members. Younger Americans are “significantly more likely” to lean Democratic, while older Americans skew Republican, Gallup finds.

Implications for the 2016 presidential election? “While an anti-same-sex marriage position should not present a challenge for GOP candidates in the primary, it could be more challenging in a general election setting given majority support among all Americans.” Like President Obama, Democratic front-runner Hillary Rodham Clinton has come around to supporting gay marriage. Republican front-runner Jeb Bush, on the other hand, has doubled-down on his opposition to such marriages.

• How one thinks about homosexuality can influence one’s opinion on gay rights generally and same-sex marriage specifically, and another recent Gallup poll seems to bear this out. Here, the trend is dramatic.

Just four years ago, Americans were evenly split on whether same-sex orientation is something gays and lesbians are born with rather than something that is determined by their upbringing or environment. Today, Gallup finds, Americans believe that sexual orientation is inherent at birth by a 51-30 percent margin.

Here too, Democrats and Democratic-leaning Independents are more likely to hold to the “born with” position (62-24 percent). But Republicans and Republican-leaning Independents are moving in this direction as well with a closer plurality accepting this view (40-36 percent).

“In addition to their changing views on the origins of being gay or lesbian, Americans' views on the morality of same-sex relations have also shifted in recent years,” Gallup finds. “Currently, a record-high 63 percent of Americans describe gay or lesbian relations as ‘morally acceptable,’ which became the majority view in 2010. Only a decade ago, a majority thought same-sex relations were morally wrong…. Notably, for the first time, a majority of Republicans believe that same-sex relations are morally acceptable. Democrats crossed the majority threshold more than a decade ago.”

• More broadly, Gallup finds, the left has caught up with the right on social ideology.

In 2009, 42 percent of those surveyed called themselves “conservative” or “very conservative. Only 25 percent said they were “liberal” or “very liberal” on social issues. Today, the question splits evenly 31-31 percent.

“The broad trend has been toward a shrinking conservative advantage, although that was temporarily interrupted during the first two years of Barack Obama's presidency,” Gallup reports. “Since then, the conservative advantage continued to diminish until it was wiped out this year.”

Here, too, demographics are involved “with younger, more liberal Americans entering adulthood while older, more conservative adults pass on.”

• It’s hard to judge the explicit political impact, but Americans greatly overestimate the number of gay men and lesbians in the US today.

“The American public estimates on average that 23 percent of Americans are gay or lesbian, little changed from Americans' 25 percent estimate in 2011, and only slightly higher than separate 2002 estimates of the gay and lesbian population,” Gallup reports in another new poll. “These estimates are many times higher than the 3.8 percent of the adult population who identified themselves as lesbian, gay, bisexual or transgender in Gallup Daily tracking in the first four months of this year.”

Gallup acknowledges the challenge it faces in making such determinations: "There are a number of ways to measure lesbian, gay, and bisexual orientation, and transgender status. Sexual orientation can be assessed by measuring identity as well as sexual behaviors and attractions."

But the polling organization also notes that some of the overestimation may reflect public lack of knowledge about social statistics and demography, which is supported by Americans' historical tendency to overestimate the prevalence of other subgroups – African-Americans and Hispanics – in the US population.

“The overestimation may also reflect prominent media portrayals of gay characters on television and in movies, even as far back as 2002, and perhaps the high visibility of activists who have pushed gay causes, particularly legalizing same-sex marriage,” according to Gallup.

In other words, it seems certain that positive entertainment portrayals and a string of same-sex marriage wins in courts have added to public perceptions and from there to political advances for gay rights. The question today is, will this trend continue in the US Supreme Court?