Either as a percent or outright count, by how much could a presidential candidate lose the popular vote and still win the election?
In theory, a candidate could win the 11 states with the most electoral votes by one vote each, not gain a single vote in the other 39 states (plus D.C.), and win in the Electoral College. I don’t have time to do the math right now.
I don’t have time either, but if anybody wants to add up the numbers, keep in mind that you minimize the % of popular vote for the winner by assuming only one voter turned out in those 11 states, and that you got 100% turnout in the other states …
Well, it’s a hypothetical question, right? 
You can get even a lower number if you assume more than one candidate getting an electoral vote.
If you assume only one vote in California , and each state (and DC) going for the other 50 candidates with 100% each (actually you can combine some states as long as the California candidate is amoung the top 3 in electoral votes)
Since no candidate has 270, the pres is decided by the House o’ Reps.
Brian
Actually, the best way to do this is to make a list of all states and D.C. by number of electoral votes. Start from the state with the fewest elector9ial votes and work upward until you reach just exactly enough states’s electorial votes to win the electorial college. Assume that in every one of those states you get exactly half the popular vote plus one vote. Assume that in every other state you don’t get a single popular vote. Then you can win the election with less than a quarter of the popular vote.
That’s how you would do it if you assumed that the voter turnout (percentage-wise) is the same in every state. In this case, Candidate B gets 100% of the vote in California, Texas, New York, Florida, Illinois, Pennsylvania, Ohio, Michigan, Virginia, New Jersey, and Georgia. The remaining states turn out 50% + 1 voter for Candidate A. In this case, you have
Candidate A - 270 electoral votes (21.62% of the popular vote)
Candidate B - 268 electoral votes (78.38% of the popular vote)
However, as was pointed out by SCSimmons above, voter turnout varying between the states can really mung things up. In the extreme case, you could have precisely one voter going to the polls in California, Texas, New York, Florida, Illinois, Pennsylvania, Ohio, Michigan, New Jersey, North Carolina, and Georgia and voting for Candidate A, and every other state with 100% of eligible voters turning out and voting for Candidate B. Then the final results are:
Candidate A - 270 electoral votes (0.000009% of the popular vote)
Candidate B - 268 electoral votes (99.999991% of the popular vote)
Ain’t democracy great?
Oh, I should mention that I’m using estimated populations for 2003 from the U.S. Census Bureau to do these calculations. I’m also assuming a two-party race for the sake of simplicity.
One vote.
Assume three candidates; let’s decide it’s Bush, Kerry, and Nader. For whatever reason, the entire state of Alaska decides to boycott the election. Ralph Nader flys to Alaska, registers as a voter, and becomes the only person in the state to vote (for himself obviously). He now has three electoral votes.
Meanwhile in the other 49 states, voter turnout hits a record high with every eligible voter going to the polls. But when the dust settles, Bush and Kerry are evenly tied, with each having an equal number of electoral votes and neither having a majority. (Nobody else voted for Nader.)
So the election gets thrown to the House of Representatives, which gets to choose between the three top candidates. I can’t think of a reason why the House would select Nader, but it is possible. So a candidate could theoretically become President with a single vote.
MikeS I think you can do better. What are the numbers if in your first scenario you get exactly one voter showing up in the states for Candidate B and 100% turnout in the states for Candidate A. I think that should get you even more of a disparity than in your second case.
The electors, not the public, actually elected the President, so the theoritical minimum popular vote is 0.
It wasn’t me!!! I hate Canidate A!!!
What about the 3-elector states? (Wyoming, N. Dakota, D.C., etc.) If one person turned out in the 5 smallest of those states (whose citizens have more power in the Electoral College than the average citizen) then all the citizens of Georgia could vote for Cand B – and Georgia has more pop. than those 5 states combined.
–Alex