Washington ? On the eve of another national election, the terms “gridlock” and “polarization” have become staples of the political vocabulary – so much so that the reality behind them often goes unexamined.

Remedying that oversight is what motivates the unusual collaboration of two think tanks, the Hoover Institution at Stanford University and the Brookings Institution in Washington, D.C., in a forthcoming volume titled “Red and Blue Nation? Characteristics and Causes of America’s Polarized Politics.”

I have not read all the essays that 15 scholars have contributed to the volume, but the lead piece by William Galston and Pietro Nivola, both of Brookings, offers a modest bit of cheer to those who despair of our democracy in this season when we are swamped by nasty, negative campaign ads.

They acknowledge that polarization is real – certainly in Congress and in some respects in the country as well. The parties are more sharply defined and constituencies are more distinct – philosophically and to some extent geographically.

But when it comes to weighing the consequences of these divisions, Galston and Nivola offer some useful counters to the prevailing pessimism.

In one powerful paragraph they set forth their refutation of the notion that polarization produces gridlock. “Whatever else the overall legislative record of recent years may show, sclerosis has not been a distinguishing characteristic,” they write.

“Reform of the welfare system, substantial tax reductions, big trade agreements, a great expansion of federal intervention in local public education, important course corrections in foreign policy, reorganization of the intelligence bureaus, a significant campaign finance law, new rules governing bankruptcy and class-action litigation, a huge new Cabinet department, massive enlargement of Medicare – for better or worse, all these milestones, and others, were achieved despite polarized politics.”

Beyond these specific measures, they find signs of convergence between the parties – at least in some ways. Republicans, they note, have become far more comfortable with “big government” programs such as Medicare drug benefits. And Democrats have swallowed tax cuts and trade agreements they originally opposed – and now make no noises about repealing them.

“There has been enough partisan convergence (albeit selective, tenuous, opportunistic or episodic) to secure pieces of legislation,” they write. The implication I draw from this is that despite the failures on Social Security, immigration and other issues, the possibility exists that the new Congress can accomplish some things.

But even these relatively upbeat scholars acknowledge certain dangers in the degree of polarization we are seeing. First, it makes it far harder to address long-term challenges such as the underfinanced condition of our Social Security and Medicare systems and the needs of the retiring baby boomers.

Second, because the divisions no longer stop at the water’s edge, it becomes far more difficult to maintain a steady course in foreign policy. The partisan nature of the Iraq debate underlines that risk.

Third, the polarization is particularly hard on the third branch of government, the judiciary. Hearings on judgeships – especially the Supreme Court – have become full-scale political campaigns, with all the nastiness we have come to expect in those races. And some Republicans have made whipping boys of sitting judges.

Finally, there is the damage that polarization does to the whole structure of trust on which any system of representative government must rest.

The authors write: “If polarized parties are what can get 120.3 million Americans to cast ballots – the largest number in U.S. history – why worry? Because a healthy civic culture ought to do more than bestir voters; it should build their trust in the nation’s political institutions. It is in this respect that, alas, querulous partisanship can become corrosive.”

As we come to the end of another down-and-dirty campaign, that is the damage we must contemplate. It matters little which party controls Congress if the people think Congress is made up of knaves and rascals, or even of well-intentioned men and women corrupted by special interests and the constant pursuit of campaign cash.

Nothing that comes out of such a Congress will be accepted as genuine or worthwhile by the citizenry. That is a lesson that campaign consultants and candidates who indulge in relentlessly negative campaigns forget.

In the end, they not only demean their opponents; they damage the very institution in which they hope to serve. What kind of victory is that?