The raw video was so grisly, and so barbaric, that the New York Times staffers who watched and edited it for online publication were made “physically ill,” according to the newspaper’s spokeswoman.

Shortly after the Times posted it in the wee hours Thursday morning, the video went viral, leading the influential Drudge Report, proliferating on Twitter, Tumblr, and other social-media sites, and dominating cable news and broadcast outlets. It also became a tricky problem for the Obama White House.

The scene of Syrian rebels standing over seven soldiers of the Syrian regular army while the rebel commander recited a bloodthirsty poem—and pointing rifles and a pistol at the heads of their prostrate, shirtless, and badly beaten prisoners—was shocking enough. Times video editors tactfully blackened the screen as the rebels—who, just like the United States government, oppose the regime of dictator Bashar al-Assad—began to execute the soldiers; the only indication of the slaughter taking place was a noisy fusillade of 10 seconds in length. Then an image flashed of the broken bodies in a mass grave.

The top of Thursday’s Times front page carried a five-column color photo of the ghastly scene, a screen-grab from the video, alongside a lead story about the horrifying footage. And, as is frequently the case, the pictures were far more powerful than the words.

“That why Human Rights Watch now has a multimedia department that extensively engages in the use of imagery as a way of conveying information and trying to increase the impact of that information,” said Carroll Bogert, executive director of external relations for the nongovernmental organization that globally investigates violations of international law and personal rights, including atrocities of war. “The tools are in the hands of everyone” who uses a smartphone and the Internet, giving them the means to document atrocities and share them with the world.

“What’s amazing to me,” Bogert told The Daily Beast, “is that the authors of [various crimes against humanity] often photograph themselves in heroic poses at the scene. That was true in the 1999 massacres of Kosovo, the guards at Abu Ghraib, and now the rebels in Syria. It’s the same kind of macho and bravado that leads the perpetrators and killers to boast about their acts—and it’s our job to make sure those pictures come back to haunt them.”

The video—which the Times reported was obtained a few days ago from “a former rebel who grew disgusted by the killings” and smuggled it out of Syria—is suddenly haunting the Obama administration, and it could not have surfaced at a more inopportune moment. For the past six days, President Obama, Secretary of State John Kerry, and other officials have been waging an all-hands-on-deck public-relations and lobbying campaign to gain congressional authorization next week to punish the Assad regime with a military strike for its illegal use of poison gas against thousands of Syrian civilians, including young children.

The potential U.S. action, probably a cruise-missile attack, is also being marketed as an early step to help the Syrian opposition—an inchoate agglomeration that apparently includes Islamic jihadists, al Qaeda members, and other avowed enemies of America—and ultimately drive Assad from power. But the president’s plan is widely unpopular domestically, and in terms of sheer impact, the Times video is not doing any favors for the campaign to sell it. It hardly matters that the executions reportedly occurred more than a year ago, in the spring of 2012—not this past April, as the Times initially claimed, while offering no explanation for its embarrassing mistake and correction.

“Because the White House and, more broadly, those arguing for direct U.S. military intervention are portraying this as a battle between ‘good guys’ and the ‘bad guys,’ to put it in crude terms, this video demonstrates that there are bad guys on both sides,” said Ed Husain, senior fellow for Middle Eastern studies at the Council on Foreign Relations. “It does make a mockery of Secretary Kerry’s praise on Wednesday [before the House Foreign Affairs Committee] for the Syrian opposition.”

Kerry, appearing Thursday night on MSNBC’s All In With Chris Hayes, was at pains to minimize the video’s influence on the debate in Washington and beyond. “No,” he insisted when Hayes asked if the killers in the video “become, by definition, our allies.” Kerry argued: “In fact, I believe that those men in those videos are disadvantaged by an American response to the chemical-weapons use because it, in fact, empowers the moderate opposition.” Kerry added that “they are not part of the opposition that is being supported by our friends and ourselves.”

Similarly, Republican Sen. John McCain of Arizona, the leading congressional voice in support of a more robust U.S. military intervention in Syria than even President Obama is proposing, all but ignored the video.

“He hasn’t put a [statement] out on it, except to point out that the moderate opposition and their military council immediately condemned it,” a McCain spokesman emailed me, citing a press release from the National Coalition of Syrian Revolution and Opposition Forces declaring that “they, and all mainstream opposition groups, condemn in the strongest possible terms any actions that contravene international law. Additionally,” the press release continued, “killing or mistreating captured soldiers, or those who have surrendered, is an affront to the hopes and principles that fueled the initial popular uprising against the Assad regime.”

But Husain said the video presents a compelling argument against such reassuring boilerplate. “The implications are that Senator McCain and others leading the charge that the Syrian opposition seeks democracy are mistaken,” he said. “Time and again, opposition fighters have shown callous disregard for human life in the same way as the Assad regime—the difference is one of proportion. These images ought to be a wakeup call for those who think Syria is headed for a better future under the rebels.”

Husain’s Council on Foreign Relations colleague, Steven Cook, who has previously supported U.S. intervention in Syria but doesn’t any longer, agreed that Thursday’s video and others like it could sway the debate. It was, after all, a series of disturbing images on August 21—of 1,400 dead Syrians, notably more than 400 children, from a sarin-gas attack apparently by their own government—that prompted Obama’s call to action in the first place.

“Think about what kind of impact the images of sarin-gas victims have had on the debate over the course of the last two and a half weeks,” Cook said. “It wasn’t the first time that has happened. There were those who wanted to intervene on humanitarian grounds well before that. But before those pictures, hardly anyone paid much attention to the idea of intervening because of the use of chemical weapons.”

In that case, as in the most recent one, a picture may indeed be worth a hundred votes in Congress.