Both the jacket and the shirt underneath appear to be too big for his frame. Extra folds in his shirt.
Compare that photo to this one from the streamer pop convention a few weeks ago.
I'm sure he's got a closet full of these suits, and there's no way to know this is the exact same jacket. But this one fits him--perfectly. Wouldn't all his suits have the same fit?
The one he wore tonight (and last night) seemed loose.
Something different about his posture too.
Also, where's his wedding band? Don't know if he ever wore one, but jewelry is removed for CT scans. If anyone needs a CT scan, it's a presidential candidate who has had multiple aneurisms.