What explains the ever-more-bitter ideological polarization that roils our politics today? Is it a reflection of an ever-more-bitterly polarized public? Or are most Americans relatively moderate and thus poorly represented by their immoderate political parties and elected representatives?

These questions have been the subject of lively debate among political scientists in recent years. Now comes Morris Fiorina, a scholar at Stanford University and the Hoover Institution, with a new book announcing its thesis in the title: Disconnect: The Breakdown of Representation in American Politics.

Fiorina is the leading exponent of the view that the public is no less moderate and no more polarized than in the past, and thus is ill-served by fervently liberal and conservative elected representatives and political activists.

The Fiorina book will not end the debate about what he has called "the myth" -- and other political scientists insist is the reality -- of a deeply polarized electorate. But the author does cite new evidence that our elected representatives cleave more dramatically to the left and right ends of the political spectrum than those they purport to represent. He also helps illuminate the causes of the undoubted polarization of political elites over the past generation while adding some insights, such as why many self-described conservative voters are less conservative than you might think.