Perhaps it is usually the case that people think an incumbent (the devil they know) is more likely to win than a new guy (the devil they don't know), simply because they're already accustomed to the first guy.

Incumbents are said to have considerable financial advantage over challengers. Being at the top of the power structure, they are better placed to finance a 2nd kick at the can, whereas a challenger doesn't have the existing power structure to help him raise money.

Whether the above is true, I don't know. I'm just mentioning it so that the rest of you can...

1. happily accept it
2. scornfully reject it
3. and fight about it

(Heh!)