Donald Trump says Taylor Swift will "probably pay a price" for backing Kamala Harris in the race for the US presidency.
The megastar dropped a social media post backing the Democratic candidate shortly after a televised debate against Trump, her Republican rival.
"I think she is a steady-handed, gifted leader," Swift wrote on Instagram. "I believe we can accomplish so much more in this country if we are led by calm and not chaos."
Trump told Fox News he was "not a Taylor Swift fan", and it was "just a question of time" before she endorsed Harris.
Swift endorsed Joe Biden in the 2020 election. Trump said she "couldn't possibly endorse Biden" this time around, "but 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."
Swift's large and loyal fan base makes her one of the most influential celebrities in the US.
Trump has previously argued she should support him.
In February, he wrote on social media that he had signed a 2018 law that helped musicians including Swift, and there was "no way" Swift could be "disloyal to the man who made her so much money".
Around the same time, some Trump supporters spread conspiracy theories suggesting Swift and her partner, NFL star Travis Kelce, were part of a Pentagon-led plot to boost Mr Biden's election prospects.
The Harris campaign is now working to capitalise on Swift's endorsement. Its online fundraising store was selling "Harris-Walz friendship bracelets" the morning after the debate, but they were quickly listed as sold out.
By 2pm on Wednesday, local time, more than 330,000 people had visited a voter registration website using a link shared in Swift's social media post, according to the US General Service Administration.
Swift signed off her social media post as "Childless Cat Lady", in reference to Trump's running mate, JD Vance, who used the term to insult senior Democrats in 2021.
Vance said he didn't expect many Americans to be influenced by a "billionaire celebrity" who is "fundamentally disconnected" from their interests and problems.
"When grocery prices go up by 20 per cent, it hurts most Americans. It doesn't hurt Taylor Swift," Vance told Fox News.
