One chart says it all:
It is emotionally satisfying for various liberal hacks and politicians to blame ideology and pressure groups for the failure of gun control in the Senate. But the reality is that Americans increasingly feel safe with a gun in the home and see it as a viable means of self-defense. Gun control bills are seen as potentially threatening that freedom. In addition, it is worth pointing out as I did in this post that crime is way, way down overall despite the increase in guns, so any attempt to limit law-abiding people from buying guns will not be popular.
And by the way, the claim that 90 percent of people favor background checks is highly misleading. As in every poll, it depends on how you ask the question, and it is also worth pointing out that the vast majority of legal gun sales already involve background checks.