I think I kinda like this explanation. Got this in an email a couple of weeks ago and it sounds about right. Guess it could be listed as joke of the day
The Rancher
While suturing a cut on the hand of a 75 year old <st1:State w:st="on"><st1lace w:st="on">Texas</st1lace></st1:State> rancher, whose
hand was caught in a gate while working cattle, the doctor struck up a
conversation with the old man. Eventually the topic got around to Obama
and his bid to be our President.
The old rancher said, 'Well, ya know, Obama is a 'post turtle'.'
Not being familiar with the term, the doctor asked him what a 'post
turtle' was.
The old rancher said, 'When you're driving down a country road and you
come across a fence post with a turtle balanced on top, that's a 'post
turtle'.'
The old rancher saw a puzzled look on the doctor's face, so he continued
to explain. 'You know he didn't get up there by himself, he doesn't
belong up there, he doesn't know what to do while he is up there, and
you just wonder what kind of a dumb ass put him up there<o></o>