Interesting. Henry Kissinger was Secretary of State, so he would normally be in the line of succession to be President.
But Kissinger was foreign born.
The Twelfth Amendment says no person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States.
Article II.1.5 says No Person except a natural born Citizen [...] shall be eligible to the Office of President;
Sounds like Kissinger would NOT have been eligible.
Which means he would have been passed over in the line of succession had it ever gotten that far. After the President pro tem of the Senate would have come the Secretary of the Treasury.