A common question is whether Rodham Clinton or Obama is more electable.
We commonly see nationwide general-election polls, but what really matters is the electoral vote.
Based on data from Survey USA that has been noted elsewhere, I provide a new way to analyze it and conclude
Clinton currently would get 280 +/- 40 electoral votes
Obama currently would get 299 +/- 51 electoral votes
Equivalently, there is an 87% chance that Obama currently leads McCain in electoral votes, and a 70% chance that Rodham Clinton leads McCain.
Read on for the analysis...
Survey USA did a series of polls in all 50 states from Feb 26 to Feb 29 to compare the results of Clinton vs. McCain and Obama vs. McCain. For each state, if one candidate led by even 0.1%, they assigned all of the electoral votes of that state to that candidate (except in the states which assign electoral votes by congressional district). Their result was
Clinton leads McCain by 276 to 262
Obama leads McCain by 280 to 258
That is, Obama gets four more electoral votes than Clinton in the Survey USA analysis.
Assigning all of the electoral votes to the leader is fine if you are working with the final election result, but it is misleading with these poll numbers. If two candidates are tied, it would be better to say that each gets half of the electoral votes, plus or minus half of the electoral votes. This more fairly takes into account the states that are close and thus could go either way in the real election.
Proceeding in that manner and combining uncertainties from all of the states (and congressional districts in Nebraska and Maine) we get:
Clinton currently would get 280 +/- 40 electoral votes
Obama currently would get 299 +/- 51 electoral votes
270 are needed to win
Obama's advantage over Clinton grows to 19 electoral votes with this more sophisticated analysis, but the difference between Obama and Clinton is well within the margin of error (which is expressed at the 95% confidence level).
There is another way to look at this. Given the margin of error and how much more than half of the electoral votes each candidate can be expected to get, we can also approximate a probability that each candidate is actually ahead. We get:
The probability that Clinton is ahead of McCain is 70%
The probability that Obama is ahead of McCain is 87%
You could also express that as McCain's has only half as much chance against Obama (13%) as he has against Rodham Clinton (30%).
If you are interested in the details, my calculations are available. There are separate sheets for Clinton vs. McCain and Obama vs. McCain. The data in black is what Survey USA provided. The blue numbers are mine.
Tomorrow I will look more deeply at the numbers in each state. What are the battlegrounds for Rodham Clinton? For Obama? Where does one candidate do better than the other?