It's not like Lucas made that up all by his self. There were several countries in europe that elected their kings.
-Denmark (until 1660)
-The Polish-Lithuanian commonwealth
-The Holy Roman Empire
-Bohemia
They all elected their monarch.
And according to the Star Wars Databank. Bail Organa is the First chairman and Viceroy of Alderaan. But considering the way Lucas likes to toss around titles without regard to what they mean, I wouldn't put much stock in that. I mean seriously Viceroy, did they even look up what it means.
It's almost as a bad as Star Trek making the Romulan empire run by a Praetor. Or having a Pro-Consul in the central government.
