Americans' opinions on same-sex marriage are shifting toward equality, a Pew poll indicates. Pictured is an anti-gay marriage protester standing in front of the Supreme Court, which is set to rule on the issue by the end of the month. Reuters

With the Supreme Court ruling on gay marriage on its way, a Pew poll of American attitudes indicates while opinions are shifting shift toward equality, the difference among Republicans and Democrats is pronounced. Beyond that rift, young Americans are the primary drivers behind the increasing public acceptance of same-sex marriage.

The Supreme Court is expected to issue its decision on Obergefell v. Hodges before its current term ends June 30, a case that could establish whether or not the Constitution requires marriage equality. When asked whether or not they believe marriage equality in the United States is inevitable, poll respondents indicated overwhelmingly they do think so, regardless of personal position on the issue.

A separate recent poll, taken by CNN/ORC, indicates Americans do not trust the Supreme Court to perform its job well on issues like gay marriage. The Pew poll did not ask for opinions on the Supreme Court.

Democrats, according to Pew, are still much more likely to favor marriage equality laws than Republicans, with 65 percent saying they are supportive. Independents tie with Democrats while just 34 percent of Republicans support same-sex marriage.

Even so, the rate of approval and support has moved to record high levels -- and at a very fast rate. Just five years ago, more people opposed the legalization of gay marriage than supported it. Now, 57 percent of adult respondents, taken together, indicate they support gay marriage: a quick rise from just over a decade ago when the overall rate of support was at 36 percent. Republican support has jumped from 19 percent approval to 34 percent. Democratic support has risen from 45 to 65 percent.

Millennials asked for their opinion on gay marriage were much more open to the idea than their older counterparts. Seventy-three percent of millennial respondents indicated support. The second biggest generation, Generation X, was at 59 percent.

For whites, aside from the religiously unaffiliated, Catholics and mainline Protestants were more accepting of gay marriage than those that identified as evangelical. Non-Hispanic whites were the most accepting at 59 percent, followed by Hispanics at 56 percent and black respondents at 41 percent. All of these groups have undergone a fast transformation in the last handful of years.

With 37 states permitting same-sex marriage, nearly 72 percent of Americans live in a state that allows gay marriage.

The Pew poll was conducted May 12-18 among 2,002 respondents. The margin of error was 2.5 percent.