My fortress has elected it's third mayor in it's sixth year, and I've got another interesting one. This one, Betca Moistdroop, actually started off as a member of the local human civilization, the Tin Unions (who have been getting trashed by the goblins in my world. Seriously, their civilization has like 160 dwarves and 16 humans, and is led by a Gorlak. Once I get my current fortress to where I want it to and go long enough without sieges, I'm going to retire it and make some human adventurers to try and fight back against the darkness.)
Anyway, this mayor first became relevant when he became the Exalted Flame of the Sweltering Sect, which basically means he was the high priest of a cult of the human god of volcanoes.
The next year got taken prisoner by the goblins for a while (practically everyone in the Tin Unions has been a goblin prisoner at some point) and then managed to flee back to the human town.
He then went wandering as a beast hunter for a while before meeting the dwarf who would become his wife, who was actually a survivor of a werecreature attack, and a member of the Ecru Wheel (my dwarven civilization)
He stayed in her hometown for 16 years before the two of them moved to my fortress, and a few months later he managed to get elected Mayor.
This is particularly interesting because this year one of my major projects was to dig out a massive temple to the eight gods that are worshiped by the dwarves of my civilization (and leaving out the god of Murder, who none of my dwarves seem to worship, though if I ever find a worshiper of him I'll probably make a hidden shrine to him somewhere) and the way I built the temple there's a main hall, four chambers on each side, and one chamber at the end for symmetry.
Also, I just noticed that I missed smoothing the pillars on the bottom left chamber. Grrr... I'm going to have to build a platform up to those...
I wasn't sure originally what I would do with the ninth chamber, but now that I've realized my mayor worships a different deity, I think it would make sense for him to establish a temple to his god in my temple complex.
So yeah, it seems that in this version the sort of dwarves who tend to end up as mayor tend to have rich backstories.