Even with all the attention devoted to Connecticut's Democratic primary, in which Ned Lamont upset Sen. Joseph Lieberman, turnout was an anemic 43 percent. It was arguably the most important race in the nation and not even half of registered Democrats bothered to vote. This group, in turn, made up barely 15 percent of the voting-age population of the state.

The unhappy effects of low turnout are clear: ever-greater polarization in the country and in Washington, which in turn has led to ever-more rancor and ever-less legislative progress.

Here's why. With participation rates of about 10 percent or less of the eligible electorate in many primaries to 35 percent or so in midterm general elections to 50 percent or 60 percent in presidential contests, the name of the game for parties is turnout — and the key to success is turning out one's ideological base. Whichever party does a better job getting its base to the polls reaps the rewards of majority status.

And what's the best way to get your base to show up at the polls? Focus on divisive issues that underscore the differences between the parties.

Not surprisingly, the partisan divide keeps increasing. Just look at Tuesday's results: Lieberman, a centrist, was unseated by Lamont, a darling of the left; in Michigan, Joe Schwarz, a moderate Republican congressman, was beaten by Tim Walberg, a bedrock conservative. It's no wonder that when Republicans and Democrats finally arrive in Washington, there's little incentive for them to do the nation's business.

So what can be done? Here's a possible solution: mandatory voting. A number of countries, including Singapore, Cyprus, Austria and Belgium, have forms of mandatory voting. But Australia, a sprawling polity like ours, provides perhaps the best example of why it bears consideration for the United States.

In the Australian system, registered voters who do not show up at the polls either have to provide a reason for not voting or pay a modest fine, the equivalent of about $15. The fine accelerates with subsequent offenses. The result, however, is a turnout rate of more than 95 percent. The fine, of course, is an incentive to vote. But the system has also instilled the idea that voting is a societal obligation.

It has also elevated the political dialogue. Australian politicians know that all their fellow citizens, including their own partisans, their adversaries' partisans and nonpartisans, will be at the polls. The way to gain votes does not come from working your base to fever pitch; it comes from persuading the persuadables, the centrists who are increasingly left out of the American political process. Appealing to the extremes is a formula for failure.

If there were mandatory voting in America, there's a good chance that the ensuing reduction in extremist discourse would lead to genuine legislative progress. These days, valuable congressional time is spent on frivolous or narrow issues (flag burning, same-sex marriage) that are intended only to spur on the party bases and ideological extremes. Consequently, important, complicated issues (pension and healthcare reform) get short shrift.There's no question that compulsory voting would be a tough sell. Congress would have to pass a law and the states would have to enforce it. Surveys on the subject regularly show substantial majorities opposed to the idea. Americans don't like compulsory anything — we value the freedom not to vote.

But going to the polls doesn't mean that you have to vote for a particular candidate. About three percent of Australians, for example, mark X on the ballot, the equivalent of "none of the above."

Mandatory voting comes with a price: a modest loss of freedom. But this would be more than balanced by the revitalization of the rapidly vanishing center in American politics.

Norman Ornstein, a resident scholar at the American Enterprise Institute, is the co-author of "The Broken Branch: How Congress is Failing America and How to Get It Back on Track." He wrote this commentary for The New York Times.