It was one of the most viral moments from Thursday's Democratic presidential primary debate.

Beto O’Rourke – whose hometown of El Paso, Texas is still recovering from a horrific mass shooting last month that left 22 people dead – highlighted his support for a mandatory buyback of assault-style weapons by saying on Thursday night: "Hell, yes, we're going to take your AR-15, your AK-47. We're not going to allow it to be used against our fellow Americans anymore."

O'ROURKE'S 'HELL YES' DEBATE STAGE VOW

Now, the former congressman from western Texas, whose star has waned on the presidential campaign trail, is trying to capitalize on the moment.

O'Rourke's campaign quickly took to Twitter minutes later to fundraise off the debate moment. Showing the picture of an assault-style weapon, the campaign tweeted "Beto has a ban for that."

The O’Rourke campaign touted late Thursday night that the two hours of fundraising off of the breakout moment was their best so far in the third quarter of this year. But the campaign has yet to specifically say how much campaign cash they hauled in during those two hours.

The fundraising surge touted by the campaign comes an an opportune time - there are only two and a half weeks left in the third quarter of fundraising. O'Rourke raised just $3.6 million in the April-June second quarter, less than half of his first quarter haul. And his Q3 numbers will be highly scrutinized.

Soon after, the campaign started selling “HELL YES WE’RE GOING TO TAKE YOUR AR-15” shirts for $30 apiece. And they’re also advertising “Beto has a ban for that” vinyl stickers for $5 each. That line is a twist on Elizabeth Warren’s “I have a plan for that” motto.

Warren’s campaign has raised funds by selling that popular T-shirt. Meanwhile, Sen. Kamala Harris, too, has capitalized on the most talked-about moment in late June’s first round of debates -- her heated exchange with former Vice President Joe Biden.

In that showdown, the former attorney general slammed Biden’s highlighting of his decades-ago opposition to federally mandated school busing, making the point personal by explaining she was a member of only the second class of black children in California to be bused to school in an effort to force desegregation.

“That little girl was me,” Harris said directly to the former vice president.

Harris's campaign quickly tweeted out a photo of their candidate as a little girl with a note saying, “There was a little girl in California who was bussed to school. That little girl was me.” Hours later they were selling tees – also for $30 per shirt – with the photo emblazed on the shirt.