before/at the the beginning of the term

• elected president fails to qualify = elected vice president, until the elected president have been qualified
• president shall not have been chosen = elected vice president, until the elected president have been qualified
• beginning of the term: president died or permanently disabled = vice president shall become president
• no president or vice president have been chosen or qualified = senate president or speaker of the house (until the two have been chosen or qualified)
• both president and vice president died or permanently disabled = senate president or speaker of the house (until the two have been chosen or qualified)
• SEC. 7, ART. 7 = the president-elect and vice president-elect shall assume office at the beginning of their terms
• SEC. 10, ART. 7 = the congress, at 10:00 in the morning of the 3rd day after the vacancy in the offices of the President and Vice President occurs, shall convene in accordance with its rules without the need of a call and within 7 days, enact a law calling for a special election to elect a President and Vice President to be held not earlier than 45 days nor later than 60 days from time of such call
• no special election shall be called if the vacancy occurs within 18 months before the date of the next presidential election
• SEC. 7, ART. 7 = before term, if the president failed to take office, the vice presidents acts as the president until the president can take it