In the 2000 senatorial campaign, dead Democratic challenger
Mel Carnahan's name remained on the ballot because he died three days after Missouri's secretary of state approved the November ballot. After such approval, state law forbids any changes to the
ballot, including the removal or addition of any
candidate's name.
The issue of a candidate dying - after the ballots had been approved - has happened several times in Missouri, including when Democratic U.S. Senate nominee Jerry Litton died in a plane crash in 1976.
Article III of the Constitution is not violated because the deceased is never elected - if the deceased receives more votes, then by state law the seat is declared vacant. Missouri law gives the Governor the authority to make an appointment and he chose to appoint Carnahan's widow - Jean Carnahan - to the vacant senate seat.
While it is rare to have a candidate die between the issuance of the official ballot and election day, every state has similar provisions. So, even though it was a rare event, Missouri state law was written to handle just such an occurrence. There was no violation of federal or state law, and John Ashcroft, the defeated incumbent, had no recourse on these grounds to challenge the results.
Relevant Missouri Revised Statutes
Death of candidate after filing deadline and before election, procedure to be followed.
115.379. 1. Whenever the only candidate of a party for nomination or election to an office at a
primary election, general election or
special election to fill a vacancy dies after the filing
deadline and before the election, his name shall be printed on the primary, general or special election ballot, as the case may be, unless another
candidate has filed for the office pursuant to the provisions of section 115.361 or a new candidate has been selected pursuant to the provisions of sections 115.363 to 115.377. Whenever any other candidate for nomination or election to an office at a primary election, general election or special election to fill a vacancy dies after 5:00 p.m. on the fourth
Tuesday prior to the election, his name shall be printed on the primary, general or special election ballot, as the case may be. The election and canvass shall proceed, and, if a sufficient number of votes are cast for the
deceased candidate to entitle the candidate to nomination or election had the candidate not died, a vacancy shall exist on the general election ballot or in the office to be filled in the manner provided by law.
United States senator--vacancy, how filled.
105.040. Whenever a vacancy in the office of senator of the United States from this state exists, the governor, unless otherwise provided by law, shall appoint a person to fill such vacancy, who shall continue in office until a successor shall have been duly elected and qualified according to law.
Sources:
http://www.moga.state.mo.us/statutes/c100-199/1050040.htm
http://www.moga.state.mo.us/statutes/c100-199/1150379.htm
http://www.cnn.com/2000/LAW/10/30/carnahan.sidebar.pol/