I am confident that McCain as President would have yielded a slightly smaller version of the catastrophe the country faces. It's hard to pinpoint exactly where the process started, but TR and the early 1900's Progressive movement is as good a place as any.
Here is a relevant quote ...
"And it happens with this as the physicians say of
consumption, that in the beginning of the illness
it is easy to cure and difficult to recognize, but
in the progress of time, when it has not been
recognized and treated in the beginning, it becomes
easy to recognize and difficult to cure."
-- N. Machiavelli from 'The Prince' (circa 1513 CE)