The singer, 31, gave her backing to the 59-year-old and her presidential campaign just after US President Joe Biden, 81, announced on Sunday was quitting his race for the White House.
Following Biden's announcement he was also giving his "full support and endorsement for Kamala to be the nominee for our party this year", Charli wrote on X: "Kamala IS brat."
kamala IS brat— Charli (@charli_xcx) July 22, 2024
Her post referred to the title of her latest album, released on 7 June, and soon after the post Harris's official campaign cashed in on the support by changing its banner on X to mimic the style of "brat".
After the alteration, it read "kamala hq" in lowercase black lettering with a lime-green background.
Charli - real name Charlotte Emma Aitchison - defined her take on the word "brat" in a video on TikTok, saying: "You're just like that girl who is a little messy and likes to party and maybe says some dumb things sometimes.
"Who feels herself but maybe also has a breakdown. But kind of like parties through it, is very honest, very blunt. A little bit volatile.
"Like does dumb things. But it's brat. You're brat. That's brat."
Video of Kamala Harris has been spliced together and set to Charli XCX's songs. (AP PHOTO)
Some of Harris's most popular quotes and video clips have now been spliced together and set to Charli's songs.
Many of the clips have been tinted in the lime green hue of the singer's "brat" album cover - or the cover is seen popping up in between clips of Harris.
One of the most used quotes in the clips is Harris telling the US president: "We did it, Joe", after he was elected in 2020 - making her the first female vice president in American history.
Harris launched her first full day of campaigning for the Democratic presidential nomination on Monday following Biden's withdrawal from the 2024 election race.
A growing number of Democrats have endorsed her to become the party's nominee in the 5 November election - and she said in her first public speech since Biden stepped down he was feeling "much better" amid his bout of COVID-19.
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