Why elephants and donkeys for Republicans and Democrats?

I've been asked this question several times before and usually find myself stumped.  Fortunately, ABC News has the answer.  First, Why an Elephant for Republicans?

Historian David Eisenbach explains how the Republican party and elephants came together.

Blame Thomas Nast, one of several people associated with the modern American conception of Santa Claus.

Next, Why a Donkey for Democrats?

David Eisenbach uncovers the origins of the donkey as a symbol of the Democratic party.

As someone with family connections to Native Americans, I've come to dislike Andrew Jackson, but I find linking the donkey to him to be appropriate and don't mind that the party has the animal for its symbol.