I don't know what it says about me and my lack of a life, but I too have been wondering whether the Simpsons were liberal or conservative.
They are the only family that goes to church, both parents are still in the home, and despite their ups and downs, the parents take efforts to stay with each other, and, in the end, Marge got her mind right about guns.
But what about Lisa? No doubt she's a granola crunching, vegetarian, liberal who can be counted on to say something negative about a lot of things that she knows nothing about.
So, after much cogitation, it dawned on me that Homer was a conservative (he listens to a Limbaugh-like radio show), and Lisa a liberal. Homer is the adult - working, paying taxes, understanding what it takes to get by in the world. Lisa is literally and figuratively a child, like most liberals, who wants to live in an unrealistic fantasy land funded by an increasing tax burden that would be impossible to maintain because those societal institutions that generate tax revenue would be long gone - either moved out or regulated out.
Perhaps I've done too much thinking about this...
I present to you the episode where Lisa, and other "intellectual elites" take over Springfield to govern it as they see fit.