An opinion piece in Tuesday’s Washington Post -- written by Mark Penn, the leading pollster of the “new Democratic” or centrist wing of the Democratic Party -- raises a critical long-term issue – one that must be faced now, even in the midst of the presidential campaign.

The question is whether, after the election, the Dems are going to fall back into the bitter internal warfare that divided the party from 2000-2003 or whether they will be able to preserve the remarkable level of unity that has been achieved during this election. Penn’s article does not directly address this question, but it inescapably arises from the ideas he presents.

Penn essentially argues that swing voters remain the irreplaceable key to any Democratic victory. In his view, these voters can still be accurately visualized as middle aged white women -- “Soccer Moms” as new Democrats used to portray them during the Clinton years. In consequence, Penn asserts that Dems should “learn a lesson from Bill Clinton” and update many of the centrist strategies Clinton employed in the 1992 and 1996 elections.

These two opinions, by themselves, are more a restatement of long-standing New Democratic perspectives than an invitation to controversy. But Penn’s article also strongly suggests two additional ideas – that Dems have to make an either/or choice between strategies to energize the base versus those that reach out to swing voters and that Kerry’s September shift to an energetic attack on the administration’s policies in Iraq was, at best, a very risky departure from a consistently centrist strategy.

One can almost visualize populist/progressive Democrats charging up to the well-worn ramparts where they fought the intellectual battles of 2000-2003 as they finish Penn’s piece and one can almost hear the rhetorical questions beginning to be fired across the ideological divide: “Hasn’t Kerry’s rebound in recent weeks proved that he needed to aggressively take Bush on about Iraq?”, “Didn’t the elections of 2002 prove Democrats have to offer clear alternatives and not come across as ‘Republicans-Lite?’ ”

These are excellent questions, and, like Penn’s initial propositions themselves, they deserve serious and thoughtful discussion after the election is over.

But before Democrats from both wings of the party reflexively sink back into the polarized atmosphere and dialog of 2000-2003, it is vital that both recognize and acknowledge the extraordinary accomplishment that the current Democratic unity represents and the overwhelming common interest that both sides have in maintaining it after November. Democratic unity was only achieved with substantial effort and compromise – Kerry was not, after all, the first choice of either the centrist or progressive wings of the party – and it represents the most important achievement of this campaign season for the future of the party in the coming years.

And, ironically, one of the clearest demonstrations of how far today’s Democratic unity has allowed the party to progress actually comes directly from the work of Penn himself and his direct counterparts on the populist/progressive wing of the Democratic community. It can be seen by comparing the opinion surveys and strategy papers prepared under Penn’s direction for the Democratic Leadership Council and the New Democratic Network in recent months with those produced by the populist/progressive Democracy Corps, headed by Stanley Greenberg and James Carville.

After the 2000 election strategy papers by these two polling and strategy groups often appeared almost systematically crafted as mirror opposites – from their initial assumptions to empirical findings. Since January of 2004, in contrast, this is emphatically no longer the case. Rather, strategy papers prepared by Penn for the New Democratic Network in recent months and those produced by Democracy Corps exhibit three distinct patterns or tiers of agreement and disagreement.

First, on many basic issues, there are now actually large areas of agreement. This is particularly notable in the areas of core Democratic values and policy preferences. Second, there are a number of areas where disagreements of fact exist, but not of basic perspective. They are the kinds of disputes that further examination of existing data and new surveys using more focused follow-up questions can in principle resolve. Finally, there remain some areas where basic disagreements do indeed exist because the research methodologies and approaches chosen reflect underlying differences in political and moral outlook.

This hierarchy of agreement and disagreement between the two wings of the Democratic Party clearly suggests a framework for how both sides can best learn to coexist after the election is over.

First, in the areas where there is already underlying agreement, these common views need to be clearly defined and formalized. These are the ideas, principles and strategies that can provide the glue to hold the party together in the coming years.

Second, in areas where there is disagreement about facts, new institutions and forums need to be created within the Democratic community where Democrats from both wings of the party can meet and work in a spirit of collaboration rather than conflict to examine these areas of disagreement and figure out how to minimize or eliminate them entirely.

Finally, in areas where there are inescapable differences based on principles and values, centrists and populist/progressives need to define certain basic standards of civility and mutual respect that both wings agree to follow and uphold.

It is by following a three-tiered approach of this kind, rather then by allowing a return to the intra-party warfare of recent years, that the Democratic Party can convert today’s hard-won unity into the foundation for long-term development and growth.

But it is vital that the vicious cycle of intra-party fratricide be broken now, before it can once again take hold. The habit of conducting internal warfare is deeply ingrained within the Democratic Party and debates about ideas will quickly spiral into bitter antagonisms after the election if a conscious effort is not made to avoid that outcome. Dems must break the mental habit of seeing debates over political strategy as inevitably representing a clash between positions that are either totally right or wrong.

The relative importance of mobilizing base voters and reaching out to swing voters, for example, may be difficult to quantify, but it is ultimately an empirical issue and not a theological one. Equally, while many Democrats may feel that challenging Bush on Iraq was the right thing to do on moral and social grounds, whether or not it will prove the best political strategy will remain a reasonable and legitimate question even after the election, one that should not be confused with the moral arguments about the war itself.

More generally, Dems must keep in mind that this election cycle has created a renewed and reinvigorated Democratic party with two candidates virtually all Democrats – and most independent voters as well - perceive as vastly superior in intellect, character, ethics and competence to the current administration. These attractive candidates are undergirded by new and powerful grass-roots mechanisms for fundraising, voter mobilization and internet-based organizing. In the long run there is no question that the preservation of the unity which made all these advances possible will be more important to the Dems future success then any potential benefits from renewed conflicts over the issues that divided the party in the recent past.