Taylor Swift has just endorsed Kamala Harris – but it’s not just her vote Harris is after, it’s her millions of fans.

Weeks before Taylor Swift endorsed Kamala Harris on Instagram, the gears had already begun to turn Swift’s millions of fans into bona-fide Harris voters.

Soon after Harris announced her intention to run for president, Irene Kim, 29, who spends as many as 14 hours a day talking to fellow Swifties online and has attended more than five of Taylor Swift’s Eras tour concerts, sprung into action. Along with other mega-fans who supported Harris, they created social media accounts, memes, montages, and newsletters, all in a bid to help their favourite candidate win the election.

I’ve been going inside the world of the Swifties ahead of the Presidential vote for the second season of BBC Radio 4’s podcast Why Do You Hate Me USA. Subscribe to the podcast for episodes soon. I’ll be investigating how the online world of social media is shaping the US election. And when it comes to social media, Taylor Swift supporters are considered leaders of the pack.

Now the executive director of the Swifties for Kamala campaign, Ms Kim decided to get involved because she wants the US to see its first female president and believes Kamala Harris will “protect our rights, the rights of our friends, our family members”.

With more than 3,500 volunteers, the Swifties for Kamala would seem like an experienced political operation. The group has even raised over $165,000 (£126,000) for the campaign since they began tracking donations from 1 August.

But Ms Kim, who says she has never participated in political campaigning like this before, thinks everyone came together in a really “natural” way. They’re using the skills she says they’ve developed – from strategising how to buy tickets for the sold-out Eras tour and auctioning off merchandise like signed Taylor Swift records – to try and swing an election.

The Swifties for Kamala group is volunteer-led and independent of the Harris campaign, but they have been in touch.

The conversations are “surprisingly more casual than you would expect”, Ms Kim tells me. They aren’t entirely about the online world either – they’re about translating that into real-world action.

“They’re [the campaign] helping facilitate things like volunteer sign-ups and helping us coordinate volunteer training,” Ms Kim says. Not just for in-person canvassing but also text and phone banking.

“We can make requests. We really wanted a photo of Doug [Kamala’s husband] standing behind Kamala so we could do the like ‘he lets her bejewelled’ joke.”

The BBC reached out to the Harris campaign for comment, but did not get a response.

The online world is a key battleground for both campaigns, and memes and videos from supporters that feel more authentic than paid-for ads could be effective at reaching younger, disengaged voters.

The army of Swifties could also be a way for the Harris campaign to go head-to-head with Donald Trump’s already very active base of supporters online. They operate a bit like a fandom too, and have proved effective at pushing out endless memes and pictures for the former president. Endorsements from – for example – tech boss Elon Musk have also sent Musk’s devoted army of followers on X Trump’s way too.

All of that keeps Donald Trump at the top of some social media feeds. But that can backfire.

In one meme, which the former president shared on social media, an AI generated image of Swift endorsed Trump.

In her Instagram post endorsing Kamala Harris, Taylor Swift specifically cited misleading images of her supporting Trump as a reason to speak now.

“It brought me to the conclusion that I need to be very transparent about my actual plans for this election as a voter. The simplest way to combat misinformation is with the truth,” she said in her post, that was liked more than 10.7m times.

Although Swift’s endorsement specifically told her fans “your research is all yours to do, and the choice is yours to make”, Swifties for Kamala is hoping that call to vote will translate into votes for Harris.

Ms Kim says the group didn’t know the endorsement was coming, but had planned for it anyway, hoping it would yield a wave of new volunteers.

Since the post, it’s been “absolutely madness in the best way”, she says.

According to Ms Kim they’ve seen a spike in voter registration activity and a “huge boost on social media” because of the endorsement. She also says it’s been a “huge morale” boost for the Swifties involved in the group.

Taylor Swift’s online supporters have a reputation too for being devoted to her whatever it takes – and that can include being ferocious to those they see as her enemies.

Will they be trolling Trump supporters? Ms Kim says the group has actually come up with guidelines of their own about this to try to stop it from happening.

“They are very specifically about conducting yourself in a way that is respectful and specifically not engaging with hate online. And that also includes not posting hate. Have a respectful conversation,” Irene tells me.

There are Swifties too who are Trump, rather than Harris supporters. Some Swifties for Trump accounts have been set up – although currently with fewer followers than Swifties for Kamala.

Several profiles belonging to Trump-supporting Taylor Swift fans have posted about her endorsement saying it hasn’t changed their mind about who they’ll vote for.

Ms Kim says they want to reach as many voters as possible – and that they hope their shared love of Swift will help them find common ground on Harris.

“We don’t want to make anyone feel like they’re isolated or alienated,” she explains. She thinks Swifties for Kamala could be especially useful in reaching “conservative women” who are “now realising the political beliefs they were raised with don’t always align with what they feel and believe”.

So, will Swifties affect the presidential race?

The group has had hundreds of thousands of views on TikTok, but that doesn’t mean those voters are even based in the US. And they might have been people already planning to vote for Kamala Harris.

Nonetheless, in an election that could be decided by just a few hundred thousand votes in a handful of states, any boost in voter registration and voter turnout could tip the scales.

Younger voters, who make up the majority of Swift’s fans, have historically had a lower voter turnout, which means that there is more room for gains.

Ms Kim thinks Swifties and their social media know-how are a secret weapon.

“I never would have imagined this in my wildest dreams. We’ve had a lot of moments where we’ve, like taken a step back to be like, I think we’re actually making a difference and that’s like really cool.”

What will happen next? And how is what unfolds in the social media world shaping the US election? Subscribe to Why Do You Hate Me USA on BBC Sounds. Episodes coming soon.

• SIMPLE GUIDE: Everything you need to know about the vote
• EXPLAINER: Seven swing states that could decide election
• ANALYSIS: Trump’s message of American decline resonates with voters
• GLOBAL PERSPECTIVE: What the world really thought of the debate
• POLLS: Who is winning the race for the White House?