But I believe these times are strikingly different from the past, and the health and well-being of our democracy is properly a matter of great concern. We owe it to ourselves and our country to reconsider our priors and at least entertain the possibility that these concerns are justified—even if it’s uncomfortable to admit it.

Let’s start with some basics. The parties in Congress are as polarized—internally unified and distinctive from one another—as any time in history. And the 2012 electorate was the most polarized ever (or at least since the start of the American National Election Studies in 1952). For perhaps the first time in American history, the two dominant ideologies have captured the two dominant political parties.

With Barack Obama in the White House and Democrats and Republicans each controlling one chamber, Congress has ceased to operate as an effective legislative body. Deliberation and compromise are scarce commodities, not the coin of the realm. The contemporary Congress bears little resemblance to the “textbook Congress” of the 1950s and 1960s or “the reform Congress” that followed. Individual members are no longer the most useful unit of analysis for understanding congressional behavior and policymaking. Parties are the key actors, and they respond more to their activist bases than to the median voter. Public approval of Congress and trust in government have plunged to record depths. Growing concerns about economic and political inequality are rooted in real increases in the concentration of income, wealth, and opportunities for influence.

None of that is controversial. But other ideas are hotly disputed among political scientists or ignored altogether.

The most important and problematic feature of today’s polarization is its partisan character. To treat polarization as “mere sorting” is to trivialize, if not miss entirely, the biggest development in recent decades. Polarization reflects first of all the striking ideological differences between the parties, evident most sharply among elected officials and among party activists, but also clearly evident among voters.

But it reflects more than just sincere ideological differences. The rough parity between the parties fuels an intense competition for control of the White House and Congress. The stakes are high, because the ideological differences are large, and because both parties have a realistic chance of gaining or maintaining control. This leads to strategic agenda-setting and voting, even on issues with little or no ideological content and a tribalism that is now such a prominent feature of American politics.

The supposed promise of linking more tightly party and ideology was that it would offer more clarity and accountability for voters. As Austin Ranney forecast in his prophetic dissent to the famous 1950 American Political Science Association Report, “Toward a More Responsible Two-Party System,” those benefits are likely to come at a high cost.* Ranney argued that more ideologically coherent, internally unified, and adversarial parties in the fashion of Westminster-style parliamentary democracy would be a disaster within the American constitutional system, because of its separation of powers, separately elected institutions, and constraints on majority rule that favor cross-party coalitions and compromise.