I have not found the phrase "at least" used between inverted commas in most examples provided by dictionaries. Do you think I should or should not use them in the following sentence:
A federal question is a question that is related, at least in part, to ...
When I read it, I feel that inverted commas are necessary. What do you think?
There is absolutely no need for inverted commas. The only places they are required are indicating dialogue and indicating quotations.