Of all the images that have flooded the national conversation since the assassination attempt on former President Donald J. Trump at a rally in Pennsylvania on Saturday, one in particular was destined to become part of history, the record of this particular national trauma. Taken by Evan Vucci of The Associated Press, it shows Mr. Trump with blood streaks on his face, fist raised in the air. Surrounded by a crouching phalanx of Secret Service agents, he seems to be rising up, while behind him, against a bright blue sky, flies an American flag.

Why this one? In part because of the front pages on which it appeared or the social feeds that it flooded; in part because it so effectively captured the import and ethos of the critical event, of defiance in the face of fear. In part because the blood and terror against the red, white and blue is an unforgettable contrast. And in part because, of all the pictures taken that day, it is the one that has become part not just of the official record, but the pop culture record.

It has been merched.

On Etsy, as of Monday morning, not even 48 hours after the shooting, there were already more than 100 listings of T-shirts, sweatshirts and mugs for sale with the picture on them, along with such slogans as “Fight,” “Not Today” and “Never Surrender.” Teleteeshirt has a version with the line “Legends Never Die.” Sebastian Gorka, the radio host and former Trump adviser, is offering a tee for $29.99 that reads “The President of America.”

And it is not simply a national phenomenon. According to The South China Morning Post, Taobao, a site owned by Alibaba, began selling “Shooting Makes Me Stronger” tees with the photo on the front within three hours of the assassination attempt. Photos of the shirts displayed in market stalls in China are popping up on Instagram. (As for the legal implications of assorted T-shirt vendors using the photo, Mr. Vucci could not be reached for comment.)

The Trump campaign itself has not joined this particular merchandising fray, but in many ways the “Fight” T-shirts are the natural evolution of the memorabilia created around Mr. Trump’s Georgia mug shot, first by the Trump team itself and then by supporters, opponents and straightforward profiteers. In those cases, the photos became identifiable symbols of otherwise almost unimaginable moments in the political cycle, moments that crystallized the emotions — good and bad — roiling the country.