Let's look first at gay marriage. As recently as 2004, President George W. Bush's campaign was able to use it as a "wedge issue" to drive up turnout among conservatives, helping him win reelection. That year, the Pew Research Center found that 60 percent of Americans opposed gay marriage, while just 31 percent favored it. Four years later, in 2008, those numbers had shifted – though the majority was still in opposition, with 51 percent opposing, and 38 percent in favor.
By 2012, however, it was a completely different story: In July, Pew found just 41 percent of Americans opposed gay marriage, while a plurality of 48 percent favored it. Some of that shift was driven by generational changes, since young people tend to be more broadly in favor of gay marriage (though support has gone up among all age groups). The bigger change, though, was demographic: The electorate has become more Democratic, more urban, more educated, less religious, and less white – and the politics surrounding many cultural issues like gay marriage have shifted accordingly.
So might those same demographic changes portend a similar shift to the left in public opinion on guns?
Well, in recent years, as previously noted, the trend has been in the opposite direction – with support for gun rights growing. In the wake of the Columbine High School shootings in 1999, Pew found that 65 percent of Americans said it was more important to control guns, while just 30 percent said it was more important to protect gun rights. By contrast, in the wake of last summer's movie-theater shooting in Aurora, Colo., just 47 percent said controlling guns should be the priority, compared with 46 percent preferring to protect gun rights.