This as confirmed by Trump himself here:
"Comrade Kamala Harris has just informed us that she will NOT do the FoxNews Debate on September 4th. I am not surprised by this development because I feel that she knows it is very difficult, at best, for her to defend her record setting Flip-Flopping on absolutely everything she once believed in, including her statements that THERE WILL BE NO FRACKING IN PENNSYLVANIA and her HORRIBLE Performance on the Border, our “Border Czar,” where millions of criminals and people from mental institutions and terrorists, have been allowed to pour into our Country, totally unchecked and unvetted. It’s called, and she LOVES IT, an OPEN BORDER!!! Rather than the debate on September 4th, I have agreed to do a Tele-Town Hall, anchored by Sean Hannity, for Fox. It will take place in the Great Commonwealth of Pennsylvania - Details to follow!"
As mentioned, he will instead be doing a tele-town hall on the date itself.
