I don't purport to be an expert on the latter question, but some time over the past three decades Democratic Party leaders simply stopped advocating for gun control. In part, gun control was a casualty of the Democrats' efforts to make their presidential candidates more electable between Walter Mondale's drubbing in 1984 and Bill Clinton's victory in 1992. In part, it represents an overall perception that it was a losing issue for Democratic candidates. Nonetheless, the shift is still somewhat stark and surprising, especially since the Democratic Party, over this same time period, has become less rural and less southern.
If you find this disheartening, what can you do? The easiest answer is political activism. One can still find the occasional politician who supports gun control -- Colorado Governor John Hickenlooper announced this just yesterday -- but this is almost always seen as an act of political heroism, while opposing gun control is seen as pandering to the National Rifle Association. There's no reason this needs to be the case. It's important to remember that the NRA, as far as I know, has never broken any laws. They simply advocate for their members' interests using very transparent political processes. As George Stephanopoulos famously said:
Let me make one small vote for the NRA. They're good citizens. They call their Congressmen. They write. They vote. They contribute. And they get what they want over time.The NRA does not own the patent on this formula. For those who wish to change the state of American gun ownership laws, the same approach should be used: If you see a politician supporting gun control, give her money. Volunteer on her campaign. Send her a letter thanking her, and then send letters to local newspapers praising her leadership. Make a particular stance on this issue the condition for your support in a primary election, and get your friends to do the same.
There's no (pardon the term) magic bullet on this issue. It's simply a matter of providing incentives to politicians. If supporting gun control is a heroic act, very few of them will do it. If it's an easy way to gin up praise and campaign support, a lot of them will.