There's Been An Unprecedented Shift In Attitudes About Gay Marriage

Since his personal endorsement of gay marriage last spring, President Barack Obama has kept up the public support, even making a historic mention of gay rights in his inaugural address last month.

But despite the rhetoric, Obama has taken few steps to influence a change of policy. That changed Friday night, as his administration weighed in with a friend-of-the-court brief in the Supreme Court case on Section 3 of the DOMA case, urging it to be struck down as unconstitutional.

"The law denies to tens of thousands of same-sex couples who are legally married under state law an array of important federal benefits that are available to legally married opposite-sex couples. Because this discrimination cannot be justified as substantially furthering any important governmental interest, Section 3 is unconstitutional," Solicitor General Donald Verrilli wrote.

Polls show that by weighing in, Obama and the White House are siding with the majority of Americans.

In the last decade — and especially in the last few years — Americans' attitude toward gay marriage has shifted dramatically.

Right after the election in November, the Pew Research Center released a report on the changing perception of gay marriage over the past decade. It found that opinion has swung from staunch opposition in 2001 — 57 percent opposed gay marriage, compared to 35 percent who were in favor — to solid support in 2012, when 48 percent polled supported gay marriage, compared to 43 percent who were opposed.

Here's a look:

"The change in attitude is certainly unprecedented," Greg Smith, a senior researcher at the Pew Research Center, told Business Insider in November.

The shift has been similar at the state level. For example, in Iowa, a moderate swing state where same-sex marriage has been legal since 2009, two Public Policy Polling surveys show a 10-point net increase in support for gay marriage over the past 16 months alone. According to the PPP survey conducted this month, 76 percent of those surveyed said the state's legalization of same-sex marriage had no effect on their lives.

What's driving support? Self-identified independent voters. Here's a look at how they've shifted in Iowa from October 2011 to February 2013:

Brett LoGiurato/Business Insider (Data: Public Policy Polling)

Along with Independents, one of the groups that was most influenced by Obama's endorsement was one that was lagging in supporting gay marriage before it: African-Americans.

According to Pew, African-American support for gay marriage has jumped 10 points in the past two years. Obama's endorsement — which looks like it came as tides were starting to turn among African-Americans — undoubtedly helped raise support by 6 points in 2012.

At the state level, however, the shift is even more pronounced. PPP surveyed Maryland two weeks after Obama gave his public endorsement in May.

What it found was incredible: In March, 56 percent of black respondents said they would vote against a gay marriage referendum that was scheduled to be on the ballot in November. Only 39 percent supported it.

But by late May, 55 percent of black voters said they planned to support it, while only 36 percent opposed it. That added up to a 36-point swing in two months. Maryland voters approved the same-sex marriage referendum in November.

PPP found a similar shift in South Carolina. Overall, the state is opposed to making same-sex marriage legal. But in September 2011, PPP found that only 15 percent of African-Americans thought it should be legal. Last December, it found that 63 percent of African-Americans believed at least civil unions should be legal.

Here's a look at South Carolina's shift in chart form:

Brett LoGiurato/Business Insider (Data: Public Policy Polling)

Religious attitudes continue to be the main driver of the opposition to gay marriage. Gallup found in a December poll that 63 percent of Americans opposed to gay marriage said they were opposed because of religious-related reasons. According to the same poll, 53 percent of respondents said they favored legalizing gay marriage, tying a record high.

The other big holdouts are conservatives and Republicans. According to Gallup, only 30 percent of Republicans think gay marriage should be legal. That compares with an astounding 73 percent of Democrats and 55 percent of Independents.

A look:

Gallup