The biggest advantage for the incumbent in elections is holding the office. Yes, you have a record that your opponent can bash in every address and, inevitably, something will happen in the course of an election campaign that reflects poorly on your administration. But, as the incumbent you are able to look like you own the position - you aren't running for office. You are the office.
Ask an outsider for a story about Ireland. Invariably, they'll recite that most Irish of clichés: the tale of the leprechaun, the fairy shoemaker, a trickster character with a large horde of gold at the end of the rainbow who promises it all to the naive man, but evades capture and escapes with the loot in the end.