Well, first of all, America was never a democracy. It's a republic...

Secondly, I think that this quotation from the original poster is faulty "People will always vote for their own self interest, which is an expanded state providing more and more benefits."

This is not true if you actually take a look at what's going on in America today. Media plays a large part in providing "information" also known as misinformation, convincing middle american red state voters that "job creators" have shared interests with them. I mean, take a look at how the Tea Party was so angry about Entitlement taxes... so middle class/lower class voters were angry about and Entitlement tax that only affects those who are really rich. This kind of thing is paradoxical. Any lower class voter who votes for the Republicans is actually voting against their fiscal advantage. This cannot be denied.