[+/-] Indicators of Democracy

Last year I asked my wife a hypothetical question:

"If sometime in the future American democracy ceased to exist, what would the historians write? Surely there would be warning signs that democracy was on its last legs... what would those signs be?"

She didn't have an answer, nor did I, but the question has been nagging me all year. So let's start a list of reasonable, measurable factors that would apply to the United States as well as any democratic country.

1. If free and fair elections at a resonable frequency to ensure that the governed support the governors is the staple of democracy, then heading this list would be electoral disruption: elections which are not so free, fair or frequent.
2. Supression of political parties and organizations that oppose the current regime.
3. Suppression of civil liberties.

There must be more... what would you add?