Joe Biden's campaign has mastered the art of making memorable merch.

As with any candidate's site,?? ??? ??? ??? the vice president's online shop is full of apparel, accessories, and other unique ways for supporters to publicly show their Biden/Harris pride. But over the past two weeks — since the New York Timesreported that Donald Trump paid just $750 in federal income taxes the year he won the presidency and another $750 his first year in office — the Biden campaign has seriously stepped up its merch game.

After seeing people express outrage over Trump's shockingly low income tax payments, Biden's campaign released buttons, stickers, and shirts that said "I Paid More In Taxes Than Donald Trump." Then following the first presidential debate on Sept. 29, the team created "Will you shut up, man?" shirts to commemorate Biden's blunt reaction to Trump.

On Wednesday night, during the first and only vice presidential debate, the team once again had a pitch perfect response to the fly that landed on Mike Pence's head mid-debate: a Biden/Harris fly swatter featuring the clever pun, "Truth Over Flies."

The Biden team has been heavily praised online for so quickly responding to the news and finding ways to take part in viral moments. Mashable spoke with Zach McNamara, merchandise director for the Biden campaign, about the team's successful merch strategy and how they've managed to brainstorm, design, and sell these products in such a timely manner.

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McNamara gave us a little behind-the-scenes peek into how the merch gets made, explaining, "When something like the tax story comes up, or we have unifying moments during debates, like we saw last night […] there is a Slack channel where we come together and start to throw out ideas. And you know, like nine out of 10 them will not work. But a lot of times one of them will."

Once the now infamous debate fly started trending on social media and the campaign tweeted an old photo of Biden holding a swatter, everything fell into place merch-wise. The team found fly swatters that were union-made in the U.S. (like all items in the store), they came up with the pun that played off of Biden's "Truth Over Lies" quote (which is featured on other campaign merch), and they created the product mockup.

Within an hour of the fly landing on Pence's head, Biden's team had the fly swatters for sale on the site. Within 24 hours, the campaign had completely sold out of them. In the end, supporters snagged nearly 35,000 swatters, and though the product had some lighthearted inspiration behind it, Biden's team hopes people focus on the deeper message it carries.

"Yes, the fly swatter thing is cute and of the moment, but what's printed on it — the allusion to truth over lies — I think is a key reason why it resonated and why we sold so many, because we consistently see that those products that feature those short, simple phrases are among our bestsellers always," McNamara said.

The "Will you shut up, man?" shirts, which featured Biden's quote atop an image of Trump's face, were also massively popular and sold out the day after the first presidential debate. But the clever merch isn't just there to make people laugh. It also helps drive current and potential supporters to explore the site, inspires them to learn more about Biden and Harris as candidates, and, of course, raises money for the campaign.

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The witty items that piggyback on viral moments clearly get a lot of attention online and are a big hit with supporters, but interestingly they're not the campaign's biggest sellers — not by a long shot.

"Biden-Harris yard signs are the most popular item on the store virtually every hour of every day, every week. And we've sold just an ungodly amount of those. Ever since we put them up the day Senator Harris's selection was announced," McNamara said.

The online store also features other items including apparel printed with Harris and Biden's go-to fashion accessories (Chuck Taylors and aviator sunglasses), virtual Animal Crossing merch, bottles of hand sanitizer with Biden's COVID-19 plan printed on the label, and several campaign collabs with professional designers.

Though the team will be winding down rolling out new production as November draws near, supporters can expect a few more surprises to hit the shop before election day.

Ultimately, the goal is to strike the perfect balance between stressing the political gravity of this election and providing some much-needed comedic relief.

"It's a very, very serious campaign. Everybody knows that. There's possibly never been a more serious time for our country, certainly in all of our lives. But that doesn't mean that we can't have some lighthearted moments," McNamara said. "Joe and Kamala themselves, they are fundamentally lighthearted people. We don't only love them for their policies and their experience and what they've done for this country. They're good people. And lighthearted and fun is not something that we get a lot in Donald Trump's America."