Reread amendment 20. You got it wrong. If there is an acting President, it would be Paul Ryan. But I don’t think anyone would try to find out. they are still trying to figure out who was President between Mar 4 and 5 1849 because Zachary Taylor wouldn’t take the oath on Sun Mar 4. Supposedly the President pro Tempore of the Senate David Acheson was “President for a day” because that was the order of succession then
Check the Presidential Succession Act. Paul Ryan would have to resign his seat in the Congress to become acting president. Al Haig was right.
The Presidential Succession Act was different in Zachary Taylor’s day.