A possible origin for the left-right divide?

[zarus tathra]

Left wing parties focus on the interests of the poor and the disenfranchised, who in developed countries are a minority and therefore not the "norm". They're certainly more numerous than the rich, but they're usually no where near the mean or the median. This makes the left undemocratic in all but the poorest states.

Right wing parties focus on the politically powerful, like the monarchs in medieval Europe. These parties are by their nature undemocratic, but not necessarily unpopular

Or it could be that the thought of a "body of Macedonian warriors" gets you all steamy inside. 

Hahahaha. But eww

Wait....   What?

Left wing parties (pretend to) care about the poor, right wing parties (pretend to) care about the rich, while center parties try to represent the middle classes, or the "mean." Fascism was all about representing what was "normal." This is also the general tendency of democracy, to obsess over what is "normal."