I've heard the following via word-of-mouth a few times over the years, and someone on CNN yesterday morning was discussing it as well:
There were four days between Richard Nixon realizing he didn't have the votes in the Senate to avoid acquittal (8/5/1974 upon
the public release of "the smoking gun" tape) and his effective resignation date (8/9/1974). Over those four days, White House Chief of Staff Alexander Haig instituted strict orders over several federal departments that any command given or request made by Nixon needed to be cleared through Haig. This was meant to be the fail-safe against Nixon doing something irreversible (e.g. launching nukes).
I believe (but don't know) that Trump is in a similar state now that Nixon was then. I believe (but don't know) that, for instance, Trump no longer has unchecked executive control over any federal department.