In a post on Instagram late on Tuesday, Swift told her more than 280 million followers that she would vote for the US vice-president in the November 5 election, in the biggest celebrity endorsement yet for Harris.

Polls show the race essentially tied between the two candidates.

"I will be casting my vote for Kamala Harris and Tim Walz in the 2024 Presidential Election. I'm voting for @kamalaharris because she fights for the rights and causes I believe need a warrior to champion them," Swift said in her post.

Swift was pictured with her cat in the post, which she signed as "childless cat lady", in a dig at Trump's running mate JD Vance, who in a 2021 interview called some Democrats "a bunch of childless cat ladies".

He has since said it was merely a "sarcastic remark".

Swift said she was impressed by Harris's running mate Tim Walz, who the singer described as someone "who has been standing up for LGBTQ+ rights, IVF, and a woman's right to her own body for decades".

Walz, who was on air on MSNBC when the endorsement was announced, said he was "incredibly grateful" and urged the singer's large fan base of "Swifties" to "get things going".

Trump on Wednesday dismissed her endorsement, saying he "was not a Taylor fan".

"It was just a question of time," Trump told Fox News in an interview.

"She's a very liberal person. She seems to always endorse a Democrat. And she'll probably pay a price for it ... in the marketplace."

Reproductive rights have become a key issue for voters since the US Supreme Court ended the constitutional right to abortion two years ago.

IVF fertility treatments have also been pushed into the spotlight since an Alabama court ruled earlier in 2024 that frozen embryos were people.

Harris, who supports abortion rights, has cast Trump as a threat to reproductive rights in the country after he appointed Supreme Court justices who helped overturn the Roe v Wade ruling in 2022.

Trump has defended the Supreme Court's abortion ruling but has said a federal abortion ban is unnecessary and the issue should be resolved at the state level.

In August, Trump posted a fake social media image of Swift asking people to vote for him in the November election.

Swift made a reference to that in her post, saying Trump's move "really conjured up my fears around AI, and the dangers of spreading misinformation".

"It brought me to the conclusion that I need to be very transparent about my actual plans for this election as a voter," she said.

Swift has supported Democrats in the past and backed President Joe Biden in 2020.

Her endorsement is the latest for Harris from the entertainment industry.