Former president Donald Trump took his bitterness over mega-pop star Taylor Swift’s endorsement of Vice President Kamala Harris to his social network, declaring in an all-caps tweet on Truth Social on Sunday, “I HATE TAYLOR SWIFT.”

The post did not mention Swift’s endorsement following Tuesday’s presidential debate, but Trump’s comment risks angering Swift’s legions of fans.

Within 15 hours of her endorsement of Harris, Swift’s much-anticipated announcement drove about 338,000 visits to Vote.gov, the federal voter registration site the singer linked to on an Instagram Story post. It is unclear how many of her fans registered to vote.

Swift broke her silence on the presidential election minutes after the end of Tuesday’s widely watched debate between Trump and Harris, with Harris the victor in most polls. Swift announced that she planned to vote for the vice president in a lengthy Instagram post signed, “Taylor Swift, Childless Cat Lady,” a reference to past comments by Trump’s running mate, Sen. JD Vance (Ohio), that the country was led by a “bunch of childless cat ladies who are miserable at their own lives and the choices that they’ve made.” The comments have reverberated with bipartisan backlash for weeks.

“I’m voting for @kamalaharris because she fights for the rights and causes I believe need a warrior to champion them. 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 wrote in a post to 284 million followers.

“Like many of you, I watched the debate tonight,” Swift wrote. “If you haven’t already, now is a great time to do your research on the issues at hand and the stances these candidates take on the topics that matter to you the most. As a voter, I make sure to watch and read everything I can about their proposed policies and plans for this country.”

Appearing the next morning on Fox News, Trump said he was not surprised by the endorsement because “she seems to always endorse a Democrat.” He predicted that Swift would “probably pay a price for it in the marketplace,” and said that he preferred Brittany Mahomes, a fitness entrepreneur who is married to Kansas City Chiefs quarterback Patrick Mahomes. Swift’s boyfriend, Travis Kelce, also plays for the Chiefs, and the women are friends. Brittany Mahomes had “liked” a post on Instagram regarding the 2024 Republican platform.

Swift, 34, one of the world’s most popular musical artists, endorsed Joe Biden in 2020. She was born in Pennsylvania, a crucial swing state.

Trump campaign spokesman Steven Cheung, asked to comment on the former president’s post, responded with a link to the results of an ABC-IPSOS poll that the campaign had tweeted Sunday morning. It found that 81 percent of adults polled said Swift’s endorsement made no difference to them, while 13 percent said they were less likely to endorse Harris because of it, and 6 percent were more likely. Those responding negatively were overwhelmingly Trump supporters, according to the poll.

That same poll showed that Harris had a slight lead over Trump in the election, but that a large margin said Harris won the debate.

As Trump’s post reverberated around the internet on Sunday, Transportation Secretary Pete Buttigieg responded with a tweet: “Cats! Dogs! Geese! Laura Loomer! Look, now he’s attacking Taylor!” a reference to false claims by Trump and Vance that Haitian immigrants in Ohio are eating their neighbors’ pets and to the former president’s association with a far-right provocateur who has made racist statements.

A spokeswoman for Swift did not respond to a request for comment.

Swift has long supported liberal causes, including LGBTQ+ rights and gun control, and has condemned racial injustice. During the 2018 midterm election season, she endorsed two Democratic candidates in her current home state of Tennessee, saying she was appalled by Republican Sen. Marsha Blackburn’s opposition to LGBTQ+ rights and the Violence Against Women Act, which addresses domestic violence and stalking.