Compulsory voting is not a new concept, either theoretically or in practice. Currently, 22 countries have laws for compulsory voting, but they are not enforced in 11. The practice creates a legal obligation for a citizen to vote in elections. If one fails to vote, he or she may be subject to punitive measures, such as fines or community service.
Recently, US president Barrack Obama brought public attention to "mandatory" voting by advocating the practice. He has defended his advocacy with an argument based upon expanding the electorate in the interest of greater democratic legitimacy.
Voter turnout in the US is quite low compared with turnout in other mature democracies. Chronic nonvoters in the US are disproportionately poor, members of minorities, and in general, socially disadvantaged. It is argued by Obama and others, that compulsory voting would increase both the size and diversity of the active electorate.
On the other hand, if voting is a right, then to simultaneously make it a legal duty, creates a moral contradiction. Hannah Arendt, influenced by Socrates' position in Apology, argues that the right to participate politically entails a person's right not to participate in any way whatsoever.
The comments above suggest but a few of the important issues in democratic theory and political participation raised by the debate over compulsory voting.
(Please see my article, "The Moral Problem of Nonvoting". The pdf is attached below.)