IMHO, it's not the word "incumbent" that's the reason why incumbents get voted in.

It's a toss-up between the fact that the incumbent is the first person on the list, and the fact that the longer line of text catches the eye and subconsciously influences your vote.

If you have no clue what you're voting for, you tend to always choose option #1.
On multiple choice questions, you always choose the longest answer when you don't have a clue which one is right.

Dave Brown
Dave Mathewson

Ha-Ha! Remind me if I ever run for AMA office to change my name to Matt Kirschenbauerstienwiczikle.