Good question

Found it at DTD:

I am really curious about something:

During the 2000 election Al Gore chose Joe Liberman as his potential Vice-President. In 2004 Joe Liberman tried to run for President and Al Gore chose NOT to endorse him and backed John Kerry.

During the 2004 election John Kerry chose John Edwards as his potential Vice-President. Yet John Kerry has now publicly supports Obama.

I am just curious as to what changed between the time these "men" chose their potential Vice-Presidents and the time that they decided to run for President? I thought when you chose a VP it was to be the best of the best...guess I was wrong.