In that case… Unless someone can muster a majority in both houses, Nancy is next in line after Pence.
Some say Woodrow Wilson’s wife was Acting President in all but name in the last years of his term.
The President steps down voluntarily in another piece of fiction even though the Acting President will be from the opposite party. “Leo will know what to do.” The Acting President is immediately faced with a crisis; and if Zoe is dead he’s “going to blow the hell out of something and God only knows what happens next.”
I think “God only knows what happens next” sums up the present-day political situation in the U.S.A.