"I sought a theme and sought for it in vain."

-- William Butler Yeats,

"The Circus Animals' Desertion"

Once more, the theme of themelessness. Cover the Democrats for any length of time and you become expert in campaigns that don't seem to be about anything. They have policies; Democrats are good at policies. But all too often the campaigns lack a message -- a sense of what the candidate's about and what he aims to do.

Democrats don't have a monopoly on such campaigns; if anyone can remember the theme of Bob Dole's 1996 presidential bid, he's probably got it mixed up with some other campaign. But John Kerry, Al Gore and Michael Dukakis -- three of the last four Democratic standard-bearers -- never really delivered a compelling message to American voters. And there were times during each of their presidential campaigns when the candidates knew it, when they sensed they weren't connecting, brought in new advisers and asked what it was they stood for. In the waning days of the Dukakis candidacy, his top aides were reduced to writing the reasons Americans supported Democrats on butcher paper taped to the headquarters walls, just to remind themselves what the campaign was about.

The insider accounts of the Kerry campaign that are emerging have a sickening familiarity to them. The Boston Globe tells of Paul Begala, who helped Bill Clinton win two presidential races, descending on Kerry headquarters, white board in hand, scribbling a dozen suggested lines of attack against George Bush on it, and imploring the campaign to choose one and stick with it. The papers are full of Kerry aides attesting that they never knew what the campaign's message was, and there are accounts of Kerry himself chafing at the confusion.

Some of that confusion flowed directly from the candidate. John Kerry's career has had genuine high points -- his leadership of Vietnam vets against the war, his blowing the whistle on the Iran-contra and the Bank of Commerce and Credit International scandals, his battle against drilling for oil in Arctic wildlife areas -- but they are triumphs of opposition, of liberalism out of power thwarting abuses of power. Kerry never settled into a stump speech in which he said what he most wanted to do if voters handed him power, what world he wanted to build with the tools of the presidency. Voters got a sense of what he wanted to stop, but not, it seems, what he wanted to start.

The themelessness isn't simply Kerry's, however, any more than it was simply Gore's or Dukakis's. Time was when the Democrats were the party of economic justice and opportunity, the party that championed emerging constituencies as well as classes: Catholics, blacks, women. They were the party of the many against the powerful, which played a lot better in the electoral arena than being the party of the one against the many. But, with the signal exception of Clinton's '92 campaign -- a brilliant mix of economic progressivism and cultural centrism -- the Democrats haven't been able to persuade enough voters to choose them as their champions for a very long time. And Clinton's ability to deliver on that promise once in office was a sometime thing. Full employment made life better for the people at the bottom of the economy. But the erosion of the decent jobs of the old industrial economy never really stopped (and, of course, has escalated greatly under Bush), and the jobs that replaced them more often than not offered lower pay, fewer benefits and less security. The Wal-Mart economy has grown on both the Democrats' and Republicans' watch.

From Ronald Reagan to Newt Gingrich and now to George Bush, the Republicans have developed a clear response to these changes: They are the party of risk, which they call "opportunity." This is most certainly not why Bush won reelection; Americans are not pining to pay for their health coverage or retirement or college tuition with no assist from their employers or their government.

Historically the Democrats have been the party of security, but that's an identity they need to reclaim. The challenge of radical Islam demands more of them than a foreign policy of realpolitik; empiricism -- while a welcome counter to Bush's indifference to fact -- is not enough. The challenge of a global labor market demands more of them than a commitment to mid-career retraining; defending the American middle class means creating the kind of global standards that the Democrats created on the national level during the 1930s and '40s, the time of their greatest popularity. That's a daunting challenge, one that requires the Democrats to think and develop a story about the new threats to the American dream. If they do they'll come up with a more plausible list of culprits -- and solutions -- than the Republicans ever will. They may even come up with a new sense of self, with a purpose, with a theme.