
Lord Pendragon |

You'll need to more clearly define what you mean by "political campaign" I think.
I have run a campaign where politics featured strongly. It was based in a single kingdom, and the PCs were members of the the Queen's Guard, aka the Crimson Falcons. There were many nobles, both foreign and domestic, with schemes afoot, and the PCs became pawns in the political landscape and would have eventually become players in their own right.
So to answer your question, they were all from the same realm, and all started in the same position, as members of the Queen's Guard, although as time passed individuals began to develop different political connections and sympathies.

Odraude |

Currently I'm running an Age of Sail/Discovery campaign set in a psuedo-Caribbean island chain where the players are ruling a colony under the charter of a Dutch West India Company-esque organization. It's been a balance of exploration, politics, dealing with the natives, and discovery that I've enjoyed.

DonDuckie |

We did a coop Birthright-inspired kingdom campaign, we were sent by Pelor church to colonize 'the Savage Continent'. One controlled law, one source, one guilds(me, also titled Lord Protector), and one temple(quit, GM took over).
We quickly told the church to bite it, and made a fortune(eventually 1 million GP/season) selling the natives as slaves and delicatesses to Rhakshasas.
We had a ruler character and an adventurer character, which we could send to explore or handle stuff.
Then we followed it with a campaign to take down the evil empire...
Good fun.