"Unlikely" events happen every day, but we're not good at factoring them into decisions. Normally we disregard events if the odds are less than 50-50--unless the result is extreme, such as a plane crash or hitting the lotto, when we often treat it as far more probable than it really is.

As a result, there's a disconnect in the current dialogue about the odds of Alaska Governor and vice presidential candidate Sarah Palin becoming President if the Republicans win November's election.

People being people, her detractors view that prospect with such alarm that they may overstate the chances of its actually happening, while her supporters tend to view it as both acceptable and unlikely.

Political passions aside (and without wishing any ill on John McCain), how likely is it, really?

One way to look at is simple: Of the 42 Presidents, nine were VPs who succeeded to office unexpectedly. But that doesn't address the question for several reasons, including that some of those Presidents served multiple terms, and that factors such as scandal and assassination are too random to forecast from previous examples.

The most neutral analysis is based on simple math, the same sort that life insurance companies use to calculate premiums. And although actuaries can argue about all sorts of factors that would change the basic mortality table calculations (cancer history vs. high quality health care), the Social Security Administration's statistics would tell you that the odds of McCain dying in the next four years are about 1 chance in 6 or 7.

That may seem to put the event into the "safely disregard" category. But, to remind you how much that reaction depends on the potential result, think about whether you'd be willing to pull the trigger in just one round of Russian Roulette. Your odds of a very bad day are about the same as those of an early end to a McCain first term.

To put the question into a more helpful context, let's look at everyday events that have about the same odds as soon swearing in President Palin:

-Kobe Bryant hitting two consecutive three-point attempts.

-On your next try, pulling a red M&M out of the bag.

-A rainy day in El Paso or San Diego. (A first-term President Palin would be twice as likely as a rainy day in Los Angeles.)

-That you will be delayed on two consecutive flights into Newark Airport.

-Escaping jail in Monopoly by rolling a double.

-That your birthday falls on a Wednesday.

-That, during a full inning of a Major League Baseball game, one of the teams hits a home run.

-That a hurricane hits Louisiana in any given year.

-That a flipped coin comes up heads three times in a row.

-That the next car you see will be black. A first term presidential funeral is more likely than the next car you see being blue, red, green or brown; it is only less likely than the next one being silver or white.

-That any three consecutive traffic lights you hit will all be red.

Speaking of red, if the country does go that way again, a first term Alaskan President is more probable than you are of catching the flu next winter or sharing a Zodiac sign with a stranger. It is also:

-Three times more likely than being dealt a 21 in Blackjack.

-Four times as likely as the next car you see being a convertible.

-Five times as likely as a woman having twins.

-Seven times more likely than meeting someone with green eyes.

-Eight times more likely than being waited on by a redhead.

Lastly, one unlikely-but-common analogy is particularly arresting. If the Republicans win, the odds of a first term President Palin would be about three times greater than the odds of a middle-aged man being left handed (the trait recedes in the population with age). Both candidates are.

Bob Rice

Bob Rice is the author of Three Moves Ahead: What Chess Can Teach You About Business, and the former C.E.O. of a tech start-up. He now runs merchant bank Tangent Capital, which he founded in 2005.

Photo by Max Whittaker/Getty Images.

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