The survey showed that support for gay marriage was driven primarily by Democrats and independents, with 72 percent and 62 percent respectively supporting the legalization of homosexual marriage. Just a third of Republicans agree, although that number is up 18 points from the 2004 survey.

The poll also showed most Americans now believing that the U.S. Constitution should trump state laws on gay marriage by nearly a 2-to-1 margin. Interestingly, both supporters and opponents of gay marriage agree on this front, evidence that both feel confident headed into the Supreme Court's deliberations.

The poll also found that fewer than a quarter of Americans now see homosexuality as "something people choose to be." Nearly three-quarters of those who do not believe homosexuality is a choice support gay marriage; by contrast, nearly seven in 10 who do see it as a decision oppose same-sex weddings.

On Monday, White House press secretary Jay Carney said that President Obama believed it was a "good thing" that attitudes were shifting on gay marriage.

"It's testimony to how far this country and how quickly this country has traveled," Carney said.