It is probably wise not to make too much of Ned Lamont’s victory over Sen. Joseph Lieberman in Connecticut’s recent Democratic senatorial primary. In the first place, Connecticut is a thoroughly liberal Northeastern state, wedged between New York and Massachusetts, and is therefore hardly a very good barometer of American public opinion in general. Secondly, this was, after all, a Democratic primary, and its results are therefore descriptive at best of Democratic opinion, even though under Connecticut’s laws some independents and Republicans could and did vote in it. Third, only 43 percent of Connecticut’s registered Democrats took the trouble to vote — which is a lot for a primary, but still only a drop in the Connecticut bucket. Finally, Lamont defeated Lieberman by just four percentage points, which is hardly a landslide.

Still, the outcome at least focuses a bright light on a debate that is now taking place in the national Democratic Party, and which is therefore of great importance not only to the party but, at least potentially, to the country as a whole. That debate, put simply, is this: Should the United States pull out of its military operation in Iraq?

For Republicans, that question is pretty well foreclosed. We are there, and in the two years and four months remaining in George W. Bush’s presidency, we are going to stay there. The military operation, and its political consequences, is going far from satisfactorily, but to its supporters the consequences of a pullout seem infinitely worse.

For the Democrats, however, the picture looks very different. It was Bush who, for better or worse, propelled us into war against Iraq, and all of its negative consequences can be laid at his door. The temptation to blame him and pull out must be well nigh unbearable. What’s more, any inclination to recommend some policy short of a total pullout (e.g., “redeploying” our forces to some safer place in the Middle East) is bound to be overwhelmed by the sheer simplicity of a complete withdrawal.

Just 34 years ago the Democrats faced a similar decision. It was 1972, and — never mind who dragged us into Vietnam in the first place — the war in Vietnam was now “Nixon’s war,” and it, too, was going badly. The Democrats who assembled for their convention that year thought they saw a matchless opportunity, and they seized it. In nominating George McGovern as their presidential candidate, they identified themselves with opposition to the war, and their slogan became “Come home, America.” True, they lost the ensuing election to Nixon by a historic margin, carrying only Massachusetts. But within three years America did indeed “come home,” and a Democratic Congress sealed Vietnam’s fate by denying it all further military aid.

Lamont’s defeat of Lieberman is being interpreted as proof that Democrats are prepared to go that route again. And no doubt about it, many of them are. But realism about the long-range consequences of a pullout must still exert a powerful influence on many wise and thoughtful Democrats. Joe Lieberman is far from alone, however silent his sympathizers in the party may currently be.

Even if the Democrats were to sweep into control of both Houses of Congress this November, and follow that up by capturing the White House in 2008, it would take a pretty rabid partisan to welcome the prospects facing the new Democratic president. Whether America’s withdrawal from Iraq occurred before his or her inauguration or (more likely) had to be carried out on his watch, he would have to cope with consequences almost unimaginably bleak. America’s reputation, for honor and even courage, would be near zero. The Middle East would be a zoo of America-hating Islamist regimes. Flush with triumph and sure of ultimate victory, Islamic terrorists would flood the Western world, and above all the United States. Iran would be only the next in a series of nuclear-armed Islamist states.

So the Democrats have some serious thinking to do. Much depends, for all of us, on what they decide.