Immovable property owners who are able to extract rents sufficient for independence from government. That is, back to pre-Jacksonian era. Of course, there is no way to get it done because it's a catch-22: people won't vote to resign their voting rights, this is why i believe collapse is imminent.
Just like "communism" (Soviet "socialism") stopped working when variety of goods in demand became so large, and life cycles of products became so short, that centralised planning no longer had any chance not to mismanage it - that is, simply due to technological change, or in communist terms, "progress of means of production", democracy seems to stop working when free speech becomes really, really free.
I'd go on to say that, as a broad generalisation, rights and liberties of the Western world that we value so much are valuable and positively contribute to society only as long as they can in reality be only used by elites.
Sadly, concept of human rights (late XVIII century) largely preceded industrialisation, and thus the prospect of exponential economic growth that will some day make "universal" rights REALLY "universal" - evaded imagination of their inventors. They saw those rights, as a matter of course, as "universal for people like themselves", just as they didn't think of them as pertaining to women - not because they were especially sexist, but because it just didn't cross their minds...