Alignment is Allegiance
Musing about alignment in D&D today, I had a realization. The very word explains its purpose - who are you aligned with? When the world is dark, do you stand with good King Osric, or with the forces of chaos?
Once you take this into an environment with plenty of moral gray - in other words, just about every poignant decision in the story - it's just the wrong tool for the job. Alignment is not about morality, it's about allegiance.
In an urban political campaign, 'good' and 'evil' could be usefully replaced with more relevant alignments, like "Royalist" or "Republican". It's not about what you should do, but who you're doing it for.