The gun vote didn't fail because a couple of red-state Democrats bolted, or even because too many senators are afraid of the National Rifle Association, or even because Sen. Pat Toomey couldn't bring along more Republicans.
Those factors help explain why the gun vote didn't clear the extraordinary bar set for it to succeed. But they're not the main reason it failed.
The gun vote failed because of the way the Senate is designed. It failed because the Senate wildly overrepresents small, rural states and, on top of that, requires a 60-vote supermajority to pass most pieces of legislation.
The Manchin-Toomey bill received 54 aye votes and 46 nay votes. That is to say, a solid majority of senators voted for it. In most legislative bodies around the world, that would have been enough. But it wasn't a sufficient supermajority for the U.S. Senate.
Of the senators from the 25 largest states, the Manchin-Toomey legislation received 33 aye votes and 17 nay votes — a more than 2:1 margin, putting it well beyond the 3/5ths threshold required to break a filibuster. But of the senators from the 25 smallest states, it received only 21 aye votes and 29 nay votes.
In response to the point made by Klein and Soltas, Ed Kilgore of Political Animal too says the structure of the Senate is fundamentally flawed, and led to the downfall of the legislation:
I would normally say "this has to change." But for this to change, the first step is for political actors and political media to recognize and draw attention to the problem. I noted late yesterday that in a long report on the Manchin-Toomey vote in The Hill, the words "filibuster" and "cloture" do not appear, even though the vote in question was actually on a motion for cloture to end a filibuster. The defeat of the measure by a Senate minority was treated as just the way things are done. That is what has to change first, before real change can come to the Senate. And frankly, any post-mortem on the failure of gun legislation, however well-meaning, that doesn't prominently mention the horrifically anti-democratic set-up of the current Senate is missing a crucial point.
Kevin Drum of Mother Jones writes that despite the public outcry following Newtown and the momentum it brought to gun control, the gun rights lobby was still able to maintain its grip on Washington:
Generic support for gun control fell from 78 percent to 44 percent over the past two decades. Over that time, the NRA persuaded the public that gun control was a bad idea, and it paid off for them today. The upward blip in support following the Sandy Hook massacre is probably fairly ephemeral, but even if it's not, 58 percent support just isn't enough to pass contentious legislation. You generally need two-thirds or more. Even 70 percent support in 1994 was only barely enough to pass a modest assault weapons ban.
That's the power of the NRA. They've worked hard to get the public on their side, and that brings politicians along automatically. They don't really need to threaten conservative senators to get their support because conservative senators already agree with them. That agreement is strong enough that even a watered-down background check bill with 90 percent public support can't overcome a filibuster, and renewal of the assault weapons ban is just flatly out of the question.
President Obama was right to call this "round one." This kind of thing is a long-term fight for public opinion, and only after you get the public firmly on your side do you have any real chance of passing serious legislation. So the question today for liberals is simple: Is this issue important enough to keep banging away on it for years on end, the way the NRA does? If not, nothing will ever happen.