It is a truism in politics that around 40 percent of Republicans will always vote for a Republican presidential candidate and about the same percentage of Democrats will vote for their party's candidate. The battle is for the middle 20 percent.

According to a new poll commissioned by the "moderate" Democratic Leadership Council (DLC), the group with which Bill Clinton successfully aligned himself, Democrats risk losing next year's presidential election because of dramatic erosion in support among white males.

Another truism is that when the nation is at peace and secure, the mushy middle tends to favor Democrats. But when it is threatened by enemies - foreign or domestic - it tends to side with Republicans. The DLC poll found that is precisely the case now. Democrats, the poll says, would do well in attacking President Bush over the economy if it weren't for the security issue.

Mark Penn, who conducted the poll, said that since Clinton left office more Americans see Democrats as the party of big government and higher taxes. Penn said the way President Bush is handling the war on terrorism has opened a large gap with Democrats on who is to be trusted on national security issues.

"If Democrats can't close the security gap, then they can't be competitive in the next election," said Penn, which is a polite way of saying that the current crop of candidates is all losers, except Joe Lieberman, who is the only one defending the toppling of Saddam Hussein and who remains far behind in the polls.

Democrats have not learned from Clinton. In 1992, faced with three straight crushing defeats by Ronald Reagan and George H.W. Bush, who ran against ultra-left candidates, Democrats decided to go with a candidate who positioned himself as a centrist. And Clinton won - twice. But just as Clinton found it difficult to resist temptation when it came to matters of the flesh, so do Democrats easily succumb to the lure of liberalism, even though it takes them down to defeat every time.

Democratic strategist and former Walter Mondale campaign manager Bob Beckel tells me that to a certain extent the appeal by Democrats to their liberal base is predictable, but "if it wasn't for Howard Dean we wouldn't be having this conversation." Dean, the most liberal among the top-tier Democratic candidates, continues to pull the rest of the pack to the left. Beckel says what Democrats ought to be talking about is "no new taxes, no more government programs and how you fuel the entrepreneurial spirit," but he says that won't happen as the candidates try to attract their liberal base by out-liberaling each other. He recalls one of his favorite Jesse Jackson lines: "It takes two wings to fly." So far, Democrats have only a left wing, which is why the DLC poll shows them having trouble getting off the ground.

President Bush seems to be practicing middle-of-the-road politics better than his opponents. He has resisted commenting on cultural issues, such as same-sex marriage, and he rarely speaks of abortion, except to repeat his campaign slogan that every child should be welcomed in life as well as in law, which is supposed to sound non-threatening and does. While his conservative base might wish for a solid conservative or two on the Supreme Court and constitutional amendments banning gay marriage, abortion and even flag burning, Bush has shown no outward sign that he will give his base what it wants. He might if he's reelected, but to talk too much about such things now would turn off the centrists and swing the middle to the Democrats.

This was the Clinton strategy. Clinton was a liberal on national health care, gays in the military, abortion and even welfare reform (which he vetoed until polls indicated the people wanted it). But he looked and sounded moderate. Bush is basically a conservative who seeks to portray himself as a non-fire-breathing moderate, except when it comes to the war on terrorism. This is where the country is, and it is where the Democratic presidential candidates and much of their leadership are not. That's the point the DLC poll tried to make, but the pleasures of ideological self-indulgence may be too much for Democrats to resist.