The single most important piece about the shameful defeat of Toomey-Manchin yesterday is this New York Times op ed by Gabrielle Giffords, who blasts Senators for basing their vote on cowardice and cold political calculation. The single most important paragraph in that piece is this one:

I am asking every reasonable American to help me tell the truth about the cowardice these senators demonstrated. I am asking for mothers to stop these lawmakers at the grocery store and tell them: You’ve lost my vote. I am asking activists to unsubscribe from these senators’ e-mail lists and to stop giving them money. I’m asking citizens to go to their offices and say: You’ve disappointed me, and there will be consequences.

Giffords concludes: “Mark my words: if we cannot make our communities safer with the Congress we have now, we will use every means available to make sure we have a different Congress.”

I don’t know if Giffords and others pushing for sensible gun reform will succeed in sustaining the energy required to keep up the pressure. But I do know that the question of whether they are able to do this is the central, overriding one. As Jonathan Bernstein wrote yesterday in a great piece, the death of Manchin-Toomey may have been a crushing defeat, but it still has the potential to lead to possible victory later. There is now a consensus piece of legislation, and an active political infrastructure, in place that can be activated at a moment’s notice if and when this debate comes up again. The history tells us that this debate will come up again.

Obama has vowed to keep up the fight. “I see this as just round one,” the president said yesterday. “You need to let your representatives in Congress know that you are disappointed and that if they don’t act this time, you will remember come election time.”

The problem, as Chris Cillizza details this morning, is twofold. First, if a shooting as horrific as the Newtown massacre isn’t enough to prod Congress to action, it’s hard to imagine what would. Second, to pass gun reform, you need to win over several red state Democrats — Max Baucus, Mark Begich, and Mark Pryor — who are up for reelection in 2014, not to mention a handful of other Republican Senators.

To the first of those, despite yesterday’s loss, the ball has now been moved substantially forward. It isn’t just that there’s now a bill and an infrastructure in place. What’s more, we’ve demonstrated that a majority (55) of the Senate can be compelled to vote to expand background checks. Only the super-majority requirement to break the GOP filibuster prevented this from passing. That is a very significant development. If and when this debate is revived, we are now a handful of Senators away from clearing the supermajority hurdle. (Of course, then there’s the House to deal with, but still.)

The second problem identified by Cillizza is definitely problematic. However, changing demographics and the Democratic Party’s shift away from worrying about offending culturally conservative downscale whites has pushed gun violence higher up on the agenda in Democratic politics, which means Dem groups will be more active in holding red state Dems accountable on guns. Yes, it’s hard to imagine that mattering on red state turf. But if intensity can be increased you could see folks keep chipping away and eventually get one or two more red state Dems (Heitkamp, for instance, who seemed genuinely conflicted) to vote Yes on at least a procedural supermajority vote, if not on the final up or down. Key to this would be a rejiggered legislative strategy. One or two purple state Republicans, such as Kelly Ayotte in rapidly suburbanizing New Hampshire, might also ultimately be gettable, particularly since cultural issues such as guns are increasingly becoming a wedge issue against Republicans. More pressure and a better legislative strategy could conceivably inch the ball forward again.

This morning, all of this looks very far fetched and very difficult, and in truth, it is, particularly since another vote on this is unlikely anytime soon. But Gabrielle Giffords, for one, appears very determined to continue testing the boundaries of what’s possible. She isn’t going away.

* Gang of Eight prepares aggressive strategy: The bipartisan Gang of Eight Senators negotiating immigration reform is laying the groundwork to push back hard on the coming campaign by the right to derail reform. Senator Lindsey Graham is vowing to define the bill “quickly,” adding: “We’re going to be aggressive in marketing the bill.”

As the gun fight showed us, the right is awfully good at defining these debates in a way that keeps intensity high on their side.

* Jobless claims inch up: Steve Benen has it in chart form.

* The gun bill failed because the Senate is undemocratic: This amazing bit of numbers crunching, from Jonathan Cohn and Eric Kingsbury, tells the whole story:

If you assume, for sake of argument, each senator represents half of his or her state’s population, then senators voting for the bill represented about 194 million people, while the senators voting against the bill represented about 118 million people. That’s getting close to a two-thirds majority in favor of the measure.

Also see Ezra Klein, who boils it down: “The gun bill failed because the Senate is wildly undemocratic.”

* Liberals target red state Senators on guns: The Progressive Change Campaign Committee is running full page ads targeting three red state Dems — Mark Pryor, Heidi Heitkamp, Max Baucus, and Mark Begich — for voting yesterday against expanded background checks. The ad hitting Pryor is right here.

The question, as noted above, is whether the left can succeed in keeping the issue alive and continuing to organize around it.

 * Could liberal groups primary cowardly Dems over guns? Democracy For America hints at backing primary challengers to Dems who voted against expanded checks:

“Democrats who were too cowardly to get on the right side of a 90-10 issue like universal background checks better believe that the progressives will remember their spinelessness on gun violence prevention come reelection time.”

Howard Dean predicted this morning that Brian Schweitzer may primary Senator Baucus over his No vote on background checks.

 * No end to the dissembling from the NRA: A statement from the NRA claims that the background check proposal would have infringed on certain transfers between friends and family members; in fact, only private sales through commercial portals would have required a check. Even in victory, the distortions continue.

* John McCain’s leadership on guns: As the Post editorial board notes today, Senator McCain also deserves credit for his handling of the issue. I’d add that McCain showed real leadership specifically in pushing back hard against the lies coming from far right Senators and the gun lobby, which he did on the Senate floor yesterday, challenging the falsehood that Toomey-Manchin would lead to a gun registry.

 * And Heidi Heitkamp fails the test of courage: Dana Milbank has an excellent piece skewering red state Dems, but particularly Senator Heitkamp, for failing the basic test of political courage during yesterday’s gun vote. Milbank flags this quote from Senator Joe Manchin, which was aimed directly at Heitkamp:

“I think there is a time in our life, a defining time in public service,” he said, “when you know the facts are on your side and walk into the lion’s den.”

Manchin — and Pat Toomey — really deserve great credit for the leadership he showed on this issue, and I fully expect that it will continue.

What else?