Former President Donald Trump on Sunday launched a fierce attack on pop star Taylor Swift, less than a week after the musician endorsed Vice President Kamala Harris.

“I hate Taylor Swift!” Trump posted in all caps on Truth Social, the website of the Trump Media & Technology Group.

Swift endorsed Harris in an Instagram post on Tuesday, shortly after the presidential debate between the two major party candidates.

“I think she is a steady, 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 the post. She also signed the caption “childless cat lady,” a reference to comments about Democratic women made by Republican vice presidential candidate J.D. Vance.

Trump had previously shared fake images of artificial intelligence on social media that showed Swift and her fans supporting him. Swift cited such images as the reason she went public with her endorsement.

The Harris-Walz campaign responded to Trump’s message on Sunday with a statement that made frequent references to Swift’s music.

“Donald Trump’s week of whining and conspiracy theories has voters on both sides of the aisle ready to forget he ever existed,” campaign spokeswoman Sarafina Chitika said in the statement. “The American people want to emerge from the chaos and division of the Trump era, leave behind the void of Trump’s broken promises, and start anew by electing Vice President Harris to ensure America’s future of opportunity will last a long time.”

It’s unclear how much impact celebrity endorsements will have on the presidential race, even for figures as popular as Swift. About a day after her endorsement of Harris, her post had generated more than 300,000 views on Vote.gov, a government website that links users to state-specific voting information.