If you want your players to be interested in fantasy politics, make sure the issues you address are ones they will be interested in, so start with the things they've been doing and look for their political implications.
Not knowing anything about your campaign I won't presume to offer specifics, but consider how politics works at two levels - the public and the personal.
At the public level, the issues boil down to a handful of questions. How are resources to be collected and distributed? (Unrestricted capitalism vs. restricted capitalism vs communism vs. socialism; toll road or sales tax?; do you want a sewer system that works or do you want lower taxes?) Which behaviors are to be encouraged, which discouraged, and in which populations? (This is easily the type of issue that will generate the most heat - c.f. gay marriage. If you don't want to split up your players, choose something less contentious, more obviously absurd to modern eyes, like sumptuary laws - laws restricting how the different classes to dress, so that nobles won't be offended by seeing commoners who happen to be rich dressed in silk and velvet.) Who is responsible for what necessary social chores? (Conscription vs. volunteer army; serfdom vs. a free peasantry vs. chattel slavery vs. indenture; guilds vs. independent operators) This group needs assistance - should laws be passed in their favor? (The Friday fast day, with fish acceptable, was instituted by the Pope to improve the lot of fishermen.) Who gets to decide these things anyway? (Dictatorship, feudalism, universal male suffrage, universal human suffrage, universal mage suffrage, constitutional monarchy, constitutional theocracy...) Don't forget that disenfranchised groups have other recourses, though many were chancy. Medieval Jews were also bankers and could sometimes influence public events by lending or withholding money (which backfired on them when they tried to collect too big a debt and the debtor decided a pogrom would be cheaper); even peasants could revolt. The femme fatale stereotype is based on the reality that a woman who has no direct power can use personal levers to move powerful men.
On the personal level, think about the vicious infighting that develops any time you get more than ten people together for the same purpose. Who gets the credit, who gets the blame, who does the actual work, who makes the profits, who makes the decisions, whose side are you on in the fight over whether Joe was right to tear down Mary's (admittedly ugly) posters?
I bet there's fault lines in the existing campaign that can be exploited, and I bet your player already has some ideas. Let him outline what he wants to accomplish; then give him opponents with incompatible goals and the means to get them, and you'll start generating stories.
