Realistically, I think there’s a good chance he’ll die in office. The dementia has visibly progressed in the last year or so. That would set off a clown show of his followers scrambling against each other to take power, similar to the Speaker debacle in the House.
In the mean time, I would expect a lot of self-aggrandizing, lashing out at critics, and settling scores. It’s hard to predict how much and specifically what damage they’d do to our institutions. The man doesn’t have an agenda beyond ego (look at how he flipped on abortion just like that), and his toadies have to play by those rules. So by nature, it won’t be an organized assault. Anybody who’s smart and disciplined enough to wage a well-organized dismantling of government is also too dangerous to the leader and his ego, and will be fired. (Like last time. He certainly hasn’t become more canny and self-aware since then.) Hence, the clown show.
In short, I’d expect a mixture of horror and comedy, likely focused on payback for the prosecutions.