Special Message
07/01/1868
https://www.presidency.ucsb.edu...
The subject was long and earnestly debated in the Senate, and the early construction of the Constitution was, nevertheless, freely accepted ...
This is a bill passed by Congress in time of peace.
I have carefully examined the bill 'to regulate the tenure of certain civil offices.'
The power of removal was incident to that duty, and might often be requisite to fulfill it.