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From when ballots are printed to Election Day

However, if either party nominee dropped out or passed away after ballots were printed, then it would be too late to officially replace them on the ballot. In that scenario, millions of Americans would cast ballots for the inactive candidate with the understanding that their Electoral College votes would really go to someone else — probably someone designated by the DNC or RNC.

"The reality is, when you vote for president, you're never voting for that person. You're voting for the elector to cast a ballot for that person at the Electoral College meeting in December," Brown said. "I would imagine what would happen is that parties would indicate to the electors who they should vote for."

From Election Day to Dec. 17

Next, let's say we make it to Election Day without incident and voters choose a new president — but then the president-elect passes away or becomes incapacitated before the Electoral College votes on Dec. 17 to make their win official. This could be a messy political situation as well.

According to the National Archives, there is no prescribed process for what to do if the president-elect dies between Election Day and the meeting of the Electoral College. (It would not automatically be the vice president-elect, as, legally, the presidential line of succession would not have kicked in yet.) So the (ex-)president-elect's electors would essentially get to pick the president. "A whole bunch of Americans don't realize that the electors are actual, real live people," Kamarck said, who could theoretically choose for themselves whom to vote for.

There is historical precedent for this: After the 1872 election, which was won by Republican Ulysses S. Grant, Democratic nominee Horace Greeley died on Nov. 29, and his electors' votes went to various other people. According to Pildes, whether this could happen again depends on the state, as some state laws address this possibility while others do not.

There have also historically been "faithless electors" who have not voted for the candidate who won their state. Some states have laws prohibiting this, but in an emergency situation, state legislatures could change the rules to allow them to do so.

It's possible that the party would coalesce around a new candidate (for example, the vice president-elect would be a logical choice) and its electors would vote en masse for that person. Brown said the DNC or RNC would likely signal to electors whom they should vote for. That could be Harris on the Democratic side or Trump's still-unannounced running mate on the Republican side. But Brown emphasized that some states would need to adjust their faithless electors laws to allow for this.

If the electors cannot agree on a single alternative and no candidate gets a majority of electoral votes, the election would fall to the House of Representatives — a procedure known as a contingent election. The Constitution stipulates that each state's House delegation would cast a single vote for president, with a majority of states required for a candidate to win, and the Senate would elect a vice president based on a majority vote of its members individually. But Brown said that this is a highly unlikely scenario, as the electors would most likely listen to guidance from their party.

From Dec. 17 to Jan. 20

If the president-elect dies or is incapacitated after the Electoral College votes but before Inauguration Day on Jan. 20, 2025, the law is clear: the vice president-elect would be inaugurated instead. The 20th Amendment to the Constitution says, in part, "If, at the time fixed for the beginning of the term of the President, the President elect shall have died, the Vice President elect shall become President."