In 2001, Americans opposed same-sex marriage by a 57% to 35% margin.

Today, the public is about evenly split.

This is due in part to generational change. Younger generations express higher levels of support for same-sex marriage.

In 2011 Pew polling, Millennials are twice as likely as the Silent Generation to support same-sex marriage.

Among people who are religiously unaffiliated, a solid majority have supported same-sex marriage since 2001...

while Catholics and white mainline Protestants have become more supportive of same-sex marriage, especially in recent years.

Support among white evangelical and black Protestants remains lower than among other groups.

Democrats have become more supportive of same-sex marriage. Support has also risen recently among Independents.

Most Republicans continue to oppose same-sex marriage.

Among self-described liberals, support for same-sex marriage has risen 10 points...

while among moderates the balance of opinion has shifted from opposition to support of same-sex marriage.

Support for same-sex marriage has also grown recently among political conservatives, though most are still opposed.