Voting for bread and circuses
Voting for bread and circuses refers to a popular belief that the common citizens in a democracy will ultimately be its undoing when they discover that they can vote for common savings to be dispersed.
It comes from a quote by Robert A. Heinlein (emphasis added):
<-correction. It depends solely on the wisdom and self-restraint of citizens... which is opposed by the folly and lack of self-restraint of other citizens. What is supposed to happen in a democracy is that each sovereign citizen will always vote in the public interest for the safety and welfare of all. But what does happen is that he votes his own self-interest as he sees it... which for the majority translates as 'Bread and Circuses.'
(found here; original source not known, but I am familiar with the quote. This source ascribes it to the character Lazarus Long in To Sail Beyond the Sunset, which is probably correct. --Woozle 12:08, 15 January 2012 (EST))
There is a similar quote attributed to Benjamin Franklin but probably not written by him:
When the people find they can vote themselves money, that will herald the end of the republic.
This idea is commonly used as an argument for:
- restricting the vote, since the "common man" cannot be trusted to make responsible decisions about the allocation of a nation's wealth.
- reducing public services and entitlements, since that is the "common people" reallocating other people's money for themselves.
The common citizens in a democracy will ultimately be its undoing when they discover that they can vote to acquire the country's wealth for their personal benefit. The United States in the early 21st century is an example of this: Lower income-earners pay a much smaller percentage of the government's tax receipts than do higher income-earners. 
- This is called progressive taxation, which actually helps sustain society.
- It is actually the upper earners who have by far the most influence over political decisions.
- Social programs and entitlements have a history of being reduced steadily, per capita, over the past few decades.
This is basically a ludicrous and poisonous argument which seems designed to appeal to the selfishness and elitism that are in plentiful supply at all levels of income.
There is no evidence to support the idea that the "commoners", or their equivalent in whatever democracy is under discussion, have been its downfall through this mechanism. Just looking at the evidence of the US, it would appear to be specific members of the upper class who have "voted themselves bread and circuses" and been the primary cause of the recent economic crisis through their support for multiple simultaneous wars (US-Iraq War, US invasion of Afghanistan), deregulation of the banking industry. and other political efforts.