2nd paragraph:
Why? Because she cannot constitutionally fill the vacancy caused by the death, resignation, impeachment and removal of any US president under whom she served.
Why? Because she cannot constitutionally fill the vacancy caused by the death, resignation, impeachment and removal of any US president under whom she served.
Correct. That is the author's hypothosis: a woman can't be VP "because she cannot constitutionally fill the vacancy caused by the death, resignation, impeachment and removal of any US president under whom she served". Once again, this has nothing to do with First Ladies or cabinet members. Forget that Hillary ever was the wife of a President or served in any federal capacity. She is a woman, and that is the author's only point.