As the nation has commemorated the 10th anniversary of the 2001 terrorist attacks, there clearly has been nostalgia for the spirit of national unity that prevailed in the wake of those horrible events.

Yet almost no one in national politics is likely to suggest American politics is going to get any closer to a civil dialogue, even if there has been a moment’s pause for the 9/11 ceremonies and events.

Analyst Stuart Rothenberg, writing in the Capitol Hill magazine Roll Call, said political scientists disagree about whether the people are themselves polarized.

At Emory University, Professor Alan Abramowitz argues that polarization among the elites in public life reflects an increasing polarization among the general public. To some extent, is the latter a bad thing? It might in turn be a reflection of a more informed public, one that pays more attention to politics than in the past.

At Stanford University, Professor Morris Fiorina argues that most Americans are centrists, but the political class has become more polarized.

But, Rothenberg said, even if the latter is true, “for the moment that doesn’t much matter. Our current system is producing ideological politicians who are sensitive to their most ideological constituents and to the heavily ideological media, not to the political center.”

That is a significant difference from the days when politicians reserved “red meat” speeches for consumption in primaries, but then moved toward the center for general elections. Or, for that matter, worked more collegially behind the scenes than they do now.

Committed conservatives and committed liberals have grievances against a political system that can’t balance the budget, on the one hand, or find paths toward national health insurance, on the other hand.

On issues such as the attacks on evolution — “treating modern science with disdain,” as Rothenberg said — there is an assumption of the worst of motives by liberals appalled by the discussion. The reverse can be found on some other issues important to conservatives.

The days of national unity in the wake of 9/11 seem far away today.