McCarthy's failing was his alcoholism.
This was discussed in the book, and the author indicated IIRC that his alcohol use was NOT a driver of his behavior until after the Army-McCarthy hearings in 1954, after which he was unfairly censured and stripped of his committee privileges, coupled with the non-stop demonization of him by the Left and their compliant (even as today) media elements.
As M. Stanton Evans (who did more original research than any other reporter on McCarthy) and also was a cub reporter when this was all going on in real time back in 1950-1954)
I believe his enemies drove him to his death. They will no doubt attempt to do the same to Donald Trump, and in his death, will attempt to treat him and dismiss him in the same fashion.
If we let them.