Jackson, N.H. ? Nine of the last 10 presidential elections have had the same important subtheme. It is no closer to being resolved now than it was the year Richard Nixon was elected.

The subtheme, of course, is the Democrats’ struggle to define themselves and to redeem their historic role in American politics. This struggle, which began in 1968, has been the leitmotif of every primary struggle for a third of a century except for 1996, when the party was happy to renominate Bill Clinton for a second term.

The 2004 election is 15 months away, but the most intriguing part of the campaign is already well under way. It is smoldering across the country, but it has broken into flames here in New Hampshire, which only five months from now holds the first primary of the political year. How it is resolved will determine not only who is the party’s nominee but also what the Democrats will stand for at a time when their GOP rivals have resolved their own internal contradictions.

For now, the issue is being distilled into a superficial question: Is Howard Dean for real? But the question goes deeper than whether the former governor of Vermont — unknown by three out of five likely Democratic primary voters, according to a nationwide poll taken this summer — can sneak up on the established Democratic contenders.

“The cultural clash has been there for some time,” Rep. Dennis J. Kucinich of Ohio, one of the Democratic presidential candidates, said in an interview this summer. “It’s just more evident now. Some want to blur the differences between the parties.”

Blurring the differences between the parties worked for the Democrats for a time; that was part of the Clinton magic. He listened to the murmurs of the bond market, slew the deficit monster, and signed a welfare bill that Republicans ate up but that many Democrats, remembering their New Deal heritage of siding with the poor and striving, choked upon.

But blurring the differences is not the Dean way. He is from a granola state, but he traffics in red meat; no Democrat in a decade has leaned left so conspicuously, so audaciously and so enthusiastically. And if his record in Montpelier doesn’t quite match the expectations he is sowing across the Connecticut River in Manchester and in other devoutly Democratic precincts, no matter. A lot of Democrats feel good hearing that old-time religion.

The intriguing thing, of course, is an issue that appears periodically in American politics, thrust to the surface like rocks in a frozen New Hampshire field by such disparate figures as the two reverends of earlier American politics, Jesse L. Jackson and Pat Robertson: Can an intoxicating new figure bring legions of new voters into American politics — and if he does, can that return a party to its historic ideological moorings?

Jackson registered as many as a million new voters but failed to keep the Democrats on the left side of the road. Robertson brought untold hundreds of thousands of religious conservatives into the GOP flock and helped keep the Republicans on the right side of the road.

The Dean difference is the $7.5 million the country doctor raised over the Internet. He did it by tapping 45,000 donors, an astonishing figure. “We’re very surprised,” he said in a conversation this summer. “We are. I wish I was so smart to say I figured out the importance of the Internet. The community found us. We didn’t find them.” Now that this “community” is found, what will it do with the power it has found, and how will the rest of the Democratic field respond?

So far Dean, Rep. Richard A. Gephardt of Missouri and Sen. Joseph I. Lieberman of Connecticut are tied for the lead among likely Democratic primary voters, according to a nationwide Zogby International poll taken this summer. Sen. John F. Kerry of Massachusetts is right behind them. Such polls hold little meaning, of course, but this one suggests that the Democrats right now can’t make up their minds about whom they want to nominate — and what they want to be.

The presence of Lieberman at the top of the lists may represent the good will the former Democratic vice presidential candidate earned for his efforts three years ago in a cause many Democrats still believe they didn’t lose. But it also shows the appetite some Democrats have for a more moderate bill of fare than that offered by Dean and Gephardt.

The Democratic Leadership Council, the modern moderates, commissioned former Clinton pollster Mark J. Penn to examine the American political scene. His conclusion shouldn’t be surprising: Democrats have to court suburban voters and middle-class families with children, a group that determines American elections and that, unfortunately for the Democrats, favors Republicans.

“Exciting the Democratic base alone will not bring enough voters into the Democratic fold,” Penn concludes. “The heart of the middle class — suburban parents — will decide whether a Democrat can defeat George W. Bush in 2004.”

That’s a persuasive argument. So is the one being posited by Dean, which can be summarized this way: Is the White House worth winning if it’s won by a pale version of the president? Those two viewpoints are what the Democratic caucuses and primaries are about. The fact that the Democrats have been asking this question since 1968 may be the best thing Bush has going for him as Republican donors stream into barbecues at his Crawford ranch.

David Shribman is a columnist for the Pittsburgh Post-Gazette.