Yes, that votes must be made is mandatory (for both president and vice-president); however, given enough time, each affected state legislature could meet to override such a vote. Whether any such vote, or override of such vote, for president and vice-president is accepted will be determined by the U.S. House of Representatives and U.S. Senate, respectively.
Morbid Political Curiosity
With all of the talk of Sen. John McCain's age and reports of heightened Secret Service protection for Sen. Barack Obama, I wonder:
Are there are any guidelines for succession if either were to die or
become incapacitated before becoming president?
[...]
If a presidential or vice-presidential candidate is incapacitated between a party's nominating convention and the meeting of the
Electoral College, the party's central committee would gather to pick
a substitute candidate. Again, what's interesting about this timeline
is that the intervening general election (that supposedly huge day
between the conventions and the Electoral College balloting) would
turn out to be fairly irrelevant. While a party would presumably feel
great pressure to appoint its vice presidential candidate as its
presidential candidate, it could probably choose someone else.
[...]
Okay, that is the long answer. The short answer is that, in the unfortunate event a candidate is incapacitated in the period between
the election and the inauguration, the party and Congress would
improvise, and disaffected individuals would take the matter to the
courts, and the Supreme Court would tell us what the rules are. And
just for fun, as it did in 2000, the court might add that its decision
has no precedential value for future elections. [Embolding added.]
However, political parties are not legislatures and state laws would apply. And, state laws are not uniform on the subject.
The Uniform Law Commission also known as the National Conference
of Commissioners on Uniform State Laws (NCCUSL) provides sources
for applicable state laws and proposed legislation on the subject.
The Uniform Law Commission (ULC, also known as the National Conference of Commissioners on Uniform State Laws), established in
1892, provides states with non-partisan, well-conceived and
well-drafted legislation that brings clarity and stability to critical
areas of state statutory law.
A non-profit, unincorporated association consi[s]ting of commissioners appointed by each state, the District of Columbia, the
Commonwealth of Puerto Rico and the United States Virgin Islands. The
purpose of this organization is to discuss and debate which areas of
the law require uniformity among the states and territories. The
NCCUSL drafts Uniform Acts accordingly. The results of these
discussions are proposed to the various jurisdictions as either model
acts (such as the Model Penal Code) or uniform acts (such as the
Uniform Commercial Code).
Using the table of state laws concerning electors and candidates,
- Iowa (death or removal before the general election)
§ 54.5 If a presidential or vice-presidential candidate dies or is removed from the ballot before the general election, the state central
committee of the political party or the governing committee of the
national party can find a substitute candidate.
- Massachusetts (death, withdrawal, or ineligibility of candidate)
MGL, ch. 53, § 8 Certificates of nomination made by convention or caucus have to include any provisions that are made for filling
vacancies in case the candidate dies, withdraws or is otherwise ruled
ineligible. State committees of the respective political parties
nominate the presidential electors. Electors have to submit an
acceptance form that includes a pledge by the presidential elector to
vote for the candidate named in the filing.
- Utah (death or felony conviction of [a] candidate)
Utah Code Ann § 20A13-304 If elector casts ballot for someone not nominated by the party of which he is an elector (except upon the
death or felony conviction of that candidate) he will be considered to
have resigned, his vote will not count, and the remaining electors
will appoint another person to fill his vacancy
- Colorado (and other National Popular Vote states)
CRS § 1-4-304 Each presidential elector shall vote for the presidential candidate and, by separate ballot, vice-presidential
candidate who received the highest number of votes at the preceding
general election in this state.
Many states require voting for "their designated party candidate"
without specifically permitting the party to replace the candidate.
Some have no specific rule.
This lack of uniformity is what would allow "disaffected individuals
[to] take the matter to the courts".
--- Due to the lack of uniformity in state laws, the ULC has prepared a draft proposal, March 2009, to address the issue.
[Note: this has not been submitted to the states.]
SECTION 7. DEATH OF WINNING PRESIDENTIAL OR VICE-PRESIDENTIAL CANDIDATES BEFORE ELECTOR MEETING.
(a) If before the meeting of electors, the winning presidential candidate dies, the political party that nominated the winning slate
of electors shall notify the [Secretary of State] that the winning
vice-presidential candidate is to be substituted as its candidate for
President, and it shall further inform the [Secretary of State] of a
substitute candidate it has selected for Vice-President. If before the
meeting of electors, the winning vice-presidential candidate dies, the
political party shall notify the [Secretary of State] of a substitute
candidate it has selected for Vice-President. If before the meeting of
electors both the winning presidential candidate and the winning
vice-presidential candidate die, the political party shall notify the
[Secretary of State] of substitute candidates it has selected for both
offices.