Look what they made her do.

Taylor Swift, who is one of America’s most celebrated pop-culture icons and has an enormous following across the world, endorsed Vice President Kamala Harris late Tuesday after Ms. Harris’s debate against former President Donald J. Trump.

The endorsement by Ms. Swift, delivered minutes after Ms. Harris and Mr. Trump had stepped off the debate stage in Philadelphia, offers Ms. Harris an unrivaled celebrity backer and a tremendous shot of adrenaline to her campaign, especially with the younger voters she has been trying to attract.

“Like many of you, I watched the debate tonight,” Ms. Swift wrote on Instagram to her 283 million followers. “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."

She signed her post as “Childless Cat Lady,” a reference to comments made by Mr. Trump’s running mate, Senator JD Vance of Ohio, about women without children. The photo that accompanied her post showed her holding a furry feline, Benjamin Button, her pet Ragdoll.

Ms. Swift’s endorsement was much anticipated among Democrats. The singer has expressed regret for not having done more to speak out about her opposition to Mr. Trump during his first run in 2016. Since then, she has embraced a more political posture while speaking out on issues such as abortion access. But the precise timing of Tuesday’s endorsement was something of a surprise: Ms. Swift endorsed Joe Biden on Oct. 7, 2020, closer to the election.

The impact of Ms. Swift’s endorsement may be hard to quantify, but her ability to get supporters to register to vote came into sharp relief just last year. In a brief post on her Instagram account in 2023, Ms. Swift encouraged her 272 million supporters at the time to vote and included a link to the website Vote.org.