Ok, just to show my mathematical understanding:
http://www.ssa.gov/OACT/STATS/table4c6.html has the actuarial life table that I used in the previous post.
Now since McCain is now 72 years old there is a 3.01% chance of him dying in the next year (assuming he is the average statistic). Now assuming the figures stay relatively the same for the during of the possible McCain presidency, the chances of him dying when he is 73 are at 3.60%, at 74- 3.95% and at 75- 4.34%. This means that in each of those years he has a 96.99%, 96.40%, 96.05%, and 95.66% chance of living through each of those respected years. To find the chances of him making it through all 4 years to his 76th birthday, you would multiply each of the percentages together.
So, when you multiply .9699*.9640*.9605*.9566 you end up with .8591 or 85.91% chance of him living to his 76th birthday. So assuming that he wins the election, that means that Palin has a 14% chance of taking over as President. This assumes that everything with McCain is in working order at this point and he is at the average condition for a 72 year old. Now, I firmly believe that the 14% is a tad misrepresented as it also doesn't account for a higher probabilty of McCain's body giving out at a time before death, thus I believe the likelihood of Palin being thrust into the Presidency is somewhere around 30-35%.
That said if McCain were to perish or step down in the first 2 years, then you would have somebody in office that is less experienced on the national stage than Obama (is at this point) taking the oath. Unfortunately for McCain, I think he just threw away his best selling point to the voters.