Nope.
What if the nominee dies?
What if the nominee is abducted by a foreign power?
What if the nominee ... (insert unusual, unlikely event preventing taking office).
Nominee?
You mean, the president-elect? The next president?
That’s what the vice-president-elect is for.
BTW, abducted by a foreign power? So, where would the Secret Service have been? Where would the “then current” president have been? That would have called for war, believe it or not, so, who in their right minds, in that “foreign power”, have undertaken an event that would have triggered certain war?