Monday marked two months since the Senate voted against expanding federal background checks for firearms customers. Friday marked six months since the Sandy Hook Elementary School massacre pushed armed violence toward the top of this year’s legislative concerns.

Both milestones slipped by without any tangible change in a dynamic that has paralyzed Congress on the issue for more than two decades: More lawmakers fear the consequences of supporting gun control than are scared of doing nothing to control guns.

And at first blush, it seems as if one senator’s decision to spend Monday with his campaign staff and a film production crew validates all of the anxieties of the working congressional majority. Maybe, but maybe not.

Sen. Joe Manchin III, the principal Democratic author of the background check expansion, won his new term by 24 points last fall and doesn’t face voters again until 2018. But instead of spending Monday searching for persuadable colleagues, he was in West Virginia taping a campaign-style TV spot to defend himself against a new wave of criticism from his old friends at the National Rifle Association.

It will go on the air within a few days to rebut the most powerful force in the gun lobby. The NRA had given him “A” ratings and plenty of campaign support over the years, but it is now spending $100,000 to air a 30-second ad across the state this week urging viewers to call Manchin’s office and tell him “to honor his commitment to the Second Amendment” and to stop “working with” President Barack Obama on the issue.

It would be an understatement to say the gun culture and disdain for the president are strong features of the state’s political complexion, so maybe Manchin has decided he can’t act fast enough to shake off the double taint.

But his move could be about more than that. He may have concluded that before he can genuinely hope to win over any of the senators seen as persuadable, he’ll have to offer evidence that they, too, can survive the NRA’s attack ad onslaught.

So fighting his own rhetorical war now, with the argument that no law-abiding gun owner’s right to bear arms would be infringed on by more background checks, is what Manchin may view as the best way to help the larger cause.

The proposal rejected in April — a majority of 55 supported it, but it needed 60 votes to triumph over a threatened filibuster — would have expanded the existing system to cover customers online and at gun shows. Non-commercial transactions, such as those between family members and over the backyard fence, would not be affected.

The language, which Manchin unveiled with Republican Sen. Patrick J. Toomey of Pennsylvania, specifically bars the government from starting a national firearms registry, although gun groups say all the mandatory record-keeping would amount to as much. They, and a potentially pivotal group of senators, say doing away with the data collection is the only way to win their support. Advocates of gun control say doing so would make the measure toothless.

Four Democrats from red states voted against the original background check proposal, and much of the subsequent lobbying has focused on two of them: Max Baucus of Montana, who has since announced his retirement, and Heidi Heitkamp of North Dakota, who would have more than five years to explain her change of heart before standing for a second term. But switches by both would still leave the measure, which had four GOP backers in April, three Republicans shy of victory.

Senate Majority Leader Harry Reid, D-Nev., has made clear that he won’t call for a do-over vote until he’s certain of winning, a prospect that for now looks essentially impossible before the fall. Under the rules, he has 18 months, until the end of the session, to revive it. The more lugubrious, if practical, approach would be to wait only until right after inevitable occurs: Another sociopath with a shady background unloads his mail-order assault weapon into a crowd of innocents at house of worship, temple of knowledge or palace of entertainment.

Until then, advocates will have to content themselves with the steady progress the Obama administration is making on its gun-control-around-the-edges, by-executive-order agenda. That’s what Vice President Joseph R. Biden Jr. will be talking about Tuesday, when he gathers a group of gun control advocates for a photo op at the White House

He’ll also reiterate his “this fight is far from over” legislative rallying cry, which he used in an email last week seeking support from Democrats on the Hill. But there’s nothing to suggest he’s found any new congressional soldiers to join his crusade, let alone enough reinforcements to win the battle on the second go-round.

In the back of his mind, the vice president will surely be hoping that some wavering senators view Manchin’s rapid response as putting steel in their spine, not retreat on their minds.