Americans are bracing for a rare presidential rematch between the two oldest candidates in US history: the 81-year-old President Joe Biden and the 77-year-old former President Donald Trump. Concerns about their age, mental fitness, and the possibility that Trump could be convicted of a felony have raised questions about what would happen if one of them dies, becomes incapacitated, or abruptly withdraws.
If Biden, as the sitting president, were to die, Vice-President Kamala Harris would assume the powers of the presidency under the 25th Amendment. However, replacing Biden or Trump as their party's presumptive nominee is more complicated. The process depends largely on when the vacancy arises—before or after the party's nominating convention, before election day, or after the winning candidate is no longer able to take the oath of office.
If a vacancy occurs before the convention, delegates would arrive largely uncommitted, and a replacement nominee would likely be chosen in a floor fight. Democrats also have a system of 'superdelegates' who could play a decisive role in subsequent rounds. Neither Harris nor Trump's eventual vice-presidential pick would automatically become the nominee, but they would be strong contenders.
On the Republican side, Trump has yet to choose a running mate. The runner-up for the Republican nomination, Nikki Haley, proved deeply unpopular with the party's base and could struggle to win over Trump's delegates. The last time a similar situation occurred was in 1968, when President Lyndon Johnson withdrew and Senator Robert F Kennedy was assassinated, leading to a chaotic convention that prompted an overhaul of the primary system.
