The fundamental problem is that at the end of the day, this is an issue that absolutely animates the right, and just doesn't animate the left that much. Like so many issues, the extremes and activists suck up so much of the oxygen, and there are way more Republicans that identify or tolerate with their extreme side than Democrats who identify with theirs.
I think most Democrats among regular people have a pretty moderate view on guns, and EVERYONE in America loves them some guns. Somehow the Democrats have to find a way to make the views of their rank and file more indicative of their stance. It wasn't that long ago that every major Democratic candidate was careful to make sure that at least some photos circulated of them with guns, hunting, whatever. Gun rights have always been a political winner in America.
I do think that a lot of Democratic candidates have a reasonable and moderate position on guns, but the shift in the party from working class to post graduate elitist has been brutal. The left voices that get amplified now consistently show:
1) A position that is unpopular even among democrats (repeal the 2nd amendment, why does anyone need a gun, etc)
2) A thorough ignorance about actual guns. They constantly don't sound like they know what they are talking about.
Now, I do think that the "any gun any time for anybody" position of the Republicans is also not representative of Republicans. But more Republicans are comfortable with it than Democrats are of their loudest voices, so it's a winner for Republicans.
Honestly, this is another one of those issues that I think about 75% of Americans roughly agree on.
