Reply #63: Because the process for electing the President is different...

[claudiajean]

..than the process for electing US Senators.

We don't directly elect the President. The Electoral College elects the President. We elect the members of the electoral college.

Members of Congress are directly elected. Each state has different rules for the procedure for removing a Representative or Senate candidate from the ballot due to disqualification prior to the election (and death is a pretty concrete disqualification), however, there is a point in the process where, for administrative reasons, the ballots cannot be reprinted, the candidate must remain on the November ballot, and the procedure for filling a vacancy must be followed post-election.