No. In a presidential election, you aren’t voting for president directly. You are voting for electors pledged to the presidential candidate of a political party. If a candidate dies or is rendered too ill to function after ballots are printed, the national committee of the party can tell electors by registered letter to vote for a different candidate. Something similar happened in 1872 when the losing candidate died before the Electoral College voted.
In Mo. Deadman Carnahan stayed on the ballot and Dems just announced who was going to be appointed.