This is not going to happen, because it is so easy to change your official state of residence--so why on earth would one gratuitously write off a state's electoral votes? *However* as I stated in an old soc.history.what-if post:
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Contrary to what some think, the US Constitution does not require that the
president and vice-president be from different states Rather, the relevant
clause of the Twelfth Amendment reads, "The Electors shall meet in their
respective states, and vote by ballot for President and Vice-President, *one
of whom, at least, shall not be an inhabitant of the same state with
themselves*..." [emphasis added]
http://www.law.cornell.edu/constitution/constitution.amendmentxii.html
The emphasized language was borrowed from the original constitutional
provision on the election of the president (Article II, Section 1).
http://www.law.cornell.edu/constitution/constitution.articleii.html#section1
Now you may say that for all practial purposes this is the same thing as
forbidding the president and vice-president to be inhabitants of the same
state. After all, no political party is going to nominate a ticket if the
electors of one state have to reject either its presidential or vice-
presidential candidate. Consequently, in practice the presidential and vice-
presidential nominee must be from separate states. Or rather, if they are
from the same state, one of them must change his legal residence upon
nomination, as Richard Cheney did from Texas to Wyoming in 2000.
*But* the Electoral College is not the only means by which a vice-president
can be chosen. There are two other ways, and each one could theoretically
open the way for a vice president of the same state as the president:
(1) Under the Twenty Fifth Amendment, when the office of vice-president
becomes vacant "the President shall nominate a Vice President who shall take
office upon confirmation by a majority vote of both Houses of Congress."
There seems no reason why this vice-president may not be of the same state as
the president. So after Agnew's resignation, I see no reason why Nixon could
not have nominated (and both houses of Congress approved) Ronald Reagan as
vice-president--without either Nixon or Reagan having to change their legal
residence. (Since Nixon is ineligible to run again in 1976, the fact that a
Nixon-Reagan ticket could not be voted for by California electors that year
is irrelevant.) Not that Nixon was likely to do so; he regarded Reagan as
"strange" and not "pleasant to be around."
http://www.nbcnews.com/id/3678121/
(2) 1836--the vice-presidential race went into the Senate. Some southern
Democrats thought that whether or not Richard Mentor Johnson really killed
Tecumseh, his domestic habits were a little too scandalous--openly living
with a light-colored African American slave woman, having children by her
that he acknowledged, and insisting that they be treated as white. Is it
just possible that enough southern Democrats in the Senate will refuse to
vote for him to let Francis Granger, a Whig and a New Yorker, be elected?
Almost certainly not; the vote was a strict 33-16 on party lines. (For one
thing,there were rumors that Granger had abolitionist sympathies; though
Whigs in the South had argued that Johnson, the "great amalgamator," had
"habitually and practically illustrated" abolitionist principles in his own
home.
http://tinyurl.com/l3ykxtq ) But if enough of them had bolted, I see
nothing unconstitutional about having two New Yorkers--Martin Van Buren and
Francis Granger--as president and vice-president, respectively.
https://groups.google.com/d/msg/soc.history.what-if/gx8oCk9wD-w/iofB_cnBSAgJ
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In two other posts in that thread, two other possibilities were noted: (1) I observed that if Nixon in 1973 didn't want Reagan, he could have chosen another Californian, Robert Finch (whom he had asked to join the GOP ticket in 1968-- at that time Nixon was a resident of New York). (2) Someone else noted that Ford could have chosen Romney in 1974, but only f Romney made clear from the beginning that he was just a placeholder vice-president and would not run in 1976.
But again, in a regular presidential election, I just don't see a party nominating two candidates who remain *legally* residents of the same state.