Taylor Swift has endorsed Kamala Harris for president, in a post on Instagram published minutes after the US presidential debate, saying the Democratic candidate would be the “warrior” to fight for the “rights and causes” she believes in.

“As a voter, I make sure to watch and read everything I can,” Swift wrote on Instagram to her 283 million followers late on Tuesday, adding: “I will be casting my vote for Kamala Harris and Tim Walz in the 2024 presidential election”.

“I think she is a steady-handed, gifted leader and I believe we can accomplish so much more in this country if we are led by calm and not chaos.”

Swift also addressed AI-generated images shared by Donald Trump in late August that falsely depicted Swift and her fans endorsing his campaign for president.

She said: “It 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.”

Swift said she had watched the debate and urged her fans to do their research on “the stances these candidates take on the topics that matter to you the most”.

She signed off “Childless cat lady,” a reference to comments made by Republican vice-presidential candidate JD Vance. The picture that appeared with the post was of Swift with her cat Benjamin Button, one of three she owns.

Speaking in 2021 to the then Fox News host Tucker Carlson, Vance called senior Democrats in Congress and the Biden administration “a bunch of childless cat ladies who are miserable at their own lives and the choices that they’ve made and so they want to make the rest of the country miserable too”.

Swift endorsed Democratic candidates in 2018 and Joe Biden in 2020, but until Tuesday was yet to back anyone in 2024.

Asked about Swift’s endorsement of Harris on Tuesday, Republican congressman Matt Gaetz said: “I love her songs, but I want to live in a world where liberals make my art and conservatives make my laws and policies.”

Some of Swift’s fanbase had already started already mobilising for Harris. The Swifties for Kamala Coalition officially launched in late August, raising more than $138,000 for the Democratic candidate in a virtual rally featuring Carole King and the senators Elizabeth Warren and Kirsten Gillibrand.

In her statement on Tuesday, Swift encouraged her fans to register to vote.

Harris’ running mate, Tim Walz, said on MSNBC he was “incredibly grateful” to Swift. “I say that as also as a cat owner, a fellow cat owner,” he said, adding that her endorsement took courage, “and that’s the kind of courage we need in America”.

In 2012, researchers at Northwestern University and the University of Maryland tried to establish the correlation, if any, between celebrity endorsements and votes.

They used Oprah Winfrey’s endorsement of Barack Obama ahead of the 2008 Democrat primary to examine whether it had any effect on the polls.

The researchers concluded that Oprah Winfrey’s endorsement was worth about a million votes for Obama, who beat his main primary challenger, Hillary Clinton, by about 270,000 votes in the states used in the sample.