All together now: We like democracy because ... why? The pathologies of the U.S. version are so obvious in the aftermath of the latest averted crisis that we need to ask ourselves whether it's worth it — and why electoral democracy hasn't self-destructed before. Should Tunisians or Egyptians opt for the Chinese model, where rational autocrats may restrict rights but where no one threatens to blow up world markets in the name of an 18th-century tax protest?
There is an answer: Democracy is self-correcting, at least where it works. The key to the process is a version of supply and demand. When a politician acts in a way that doesn't serve the voters' interests or desires, demand for that person's services should decline. Another candidate who fills the demand will get elected.
Some democratic systems do this at the level of the individual candidate, some at the level of the party. In a winner-take-all district-based system as in the U.S. Congress, the market is structured to drive elected officials toward the median voters in their districts, and a two-party system usually emerges.