I'll have to disagree with the two of you. Just after the debate had ended Swift launched her endorsement, and will have caught the attention of millions of young fans and their parents. I think her middle paragraph speaks to the timing:

Recently I was made aware that AI of ‘me’ falsely endorsing Donald Trump’s presidential run was posted to his site. 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. The simplest way to combat misinformation is with the truth.

In order to let her fans have accurate information, so they're not seeing her tangled in confusing AI versions in the future, launching this endorsement now trumps (!) any GOP application of fake endorsements. It is crystal clear. And love or hate her music, she is a principled young woman with great influence who is trying to make a difference. She's the one who donates hugely to food banks in any community where she performs, who pays her entire staff and road crew well, and who makes a lot of charitable donations based upon circumstances she encounters.

Harris got his goat - in particular when she invited people to attend one of his rallies. Jon Stewart (The Daily Show) got the screen shot when she scored a direct hit on his ego and he said he had to "clarify" and talk about his events, and then, bizarrely, about dogs being eaten by immigrants in Ohio. He's a lunatic.

I rest my case.