THE BAD NEWS for Saddam Hussein is that most Americans are prepared to accept a war in the Middle East.

The disturbing news for George Bush is that public opinion will not sustain a long and bloody engagement. If there is support for war, it is for a short one -- which may not be the kind of war that can be fought.

The tragic news for Iraqi soldiers and, perhaps, for Iraq's civilian population, is that if the United States does wage war, pressure will be strong for the immediate use of overwhelming force.

It is possible to assert these things now, because never before in American history has the public's response to a potential armed conflict been measured with such frequency or in such detail. In the four months since Iraq's invasion of Kuwait, the polling industry has probed almost every conceivable nuance of opinion -- pressing for doubts, plumbing the depth of support for the president and asking the average citizen to choose among a broad menu of policy options.

The mood that emerges from all these studies is not of heroic flag-waving or boundless enthusiasm for a bold adventure. Memories of Vietnam are still too fresh for that. Rather, Americans seem to be expressing a stoic acceptance that war may prove impossible to avoid. In the short-term, this gritty mood works in Bush's favor; but it is not likely to sustain a long, bloody or ambiguous struggle.

Here are some things those polls have found:

Persian Gulf hawks currently outnumber doves by better than 2-to-1, but a large group of Americans are neither, according to a computer analysis of the public's response to eight key questions asked in a recent Washington Post-ABC News Poll. Roughly 50 percent of Americans consistently support Bush's approach, including the possibility of war. About 20 percent are just as consistent in opposing Bush and opposing war. In the middle sit about 30 percent of Americans who remain ambivalent in their views of Bush, war -- or both. If war actually comes, this group will likely rally to the president early but also will be quick to jump ship.

The strongest hawks are yuppie men: white, affluent, male college graduates between the ages of 26 and 44. Included in their ranks are many of the baby-boom generation that led the protest against the Vietnam War. Opposition is strongest among women, blacks, the less affluent and the less educated. This pattern is strikingly similar to the structure of opinion that existed at the beginning of the Korean War and during the early days of Vietnam -- wars on which the public eventually turned sour.

Two out of three Americans believe the United States should use all means, including the use of military force, to get Iraq out of Kuwait, a level of support unchanged since early October. While Americans may debate the details of policy, support for the Bush administration's primary policy objective remains strong.

Despite Saddam's release of the hostages, six out of 10 Americans continue to support military action against Iraq sometime after the Jan. 15 deadline for an Iraqi withdrawal. About half the country currently would begin military action against Kuwait the very moment that the U.N. deadline expires. And many of those who favor giving sanctions more time to work say they don't want to wait for long, a month or two at most -- though of course they might be willing to extend the deadline if the threat of war were imminent.

If Saddam Hussein has a hole card, it is to make so many concessions, and thus narrow the issues, that Americans are no longer certain what they are fighting for. An NBC-Wall Street Journal poll earlier this month found a 51-to-39 percent majority of voters saying that the United States should accept a deal under which Iraq would withdraw from Kuwait in exchange for concessions on control of a disputed oil field on the Iraq-Kuwait border.

Still, recent headlines to the contrary, support for Bush and stand-tough Middle East policies remains strong and deep. True, approval for Bush's handling of the gulf crisis is down roughly 20 percentage points, to about 60 percent, since the initial high mid-August readings. But even that decline doesn't necessarily suggest the public has been spooked by Bush's often artless saber-rattling.

In fact, Post-ABC Polls have found that about half of Bush's critics oppose him for not moving fast enough against Iraq. When this group is added to Bush's outright supporters, about three out of four Americans would appear to favor Bush policies or harsher measures against Saddam. That puts support for a tough line roughly where it was at the beginning of the crisis.

The problem faced by analysts of public opinion on virtually any subject is that most poll findings present them with stark yes/no choices. On many questions, the public's responses tend toward the sensible "Yes, but" or "No, if." Depending on how questions are framed, support for a hard line can be depressed to the 40 to 50 percent range or increased to 70 to 80 percent.

In assessing such numbers, the president needs to ask: How much support does he need to take the country to war? And how long will that support last? The answer to those questions may lie less in what the polls currently measure than in how, if war starts, the military performs -- and how many people, especially how many Americans, die.

Historically, even presidents pulling a divided public into war generally benefit from the sort of rally-'round-the-colors effect that inflated Bush's popularity at the beginning of this crisis. But that effect can disappear quickly. And presidents who preside over wars that go badly usually run into trouble. Abraham Lincoln thought he would lose the 1864 election because of opposition to the carnage of the Civil War until William T. Sherman and Phil Sheridan pulled some victories out of the hat in the months before the voting.

Analysts of public opinion disagree over exactly how much time Bush would have after the start of a war before he loses majority support. But almost all agree that he wouldn't have much.

"If you begin with 60 percent support or 55 percent, it's not the formula for sustained domestic support over rocky times," said Tom Mann, director of political studies for the Brookings Institution.

John Mueller, an expert on public opinion and war at the University of Rochester, thinks almost everything would have to go perfectly -- and be accomplished with lightning speed. "A week, a few weeks or perhaps a month of fighting with relatively light casualties that produced a victory would probably be acceptable," he said. "But if there were a lot of casualties, say thousands of deaths, then Bush's presidency would be in major trouble and I think there would even be calls for impeachment."

Others give Bush a little more time -- but not enough to make him feel comfortable.

"I think the structure of public opinion is there to sustain support for up to six months," said Everett Ladd, director of the Roper Center for Public Opinion Research at the University of Connecticut. "Beyond that, people will begin to feel they were deceived." Ladd, by the way, is among those analysts who believe that public support for war is truly strong.

William Schneider, a public opinion analyst at the American Enterprise Institute, argues that all this is quite predictable from the shifts in public opinion that took place as a result of the Vietnam War: "Americans learned two lessons from Vietnam which seemed inconsistent, and each party has learned one of them. They can be summarized as: Win or Get Out."

The Democrats, he said, learned the second half: That in their guts, Americans are not interventionists. The Democrats thus became, by and large, the party of peace, though Schneider notes that in the case of Iraq, "they're packaging it as patience" by urging that sanctions be given more time.

"The Republican lesson," Schneider went on, "was that Americans don't fight limited wars. We don't like them. We don't do them well. That's the 'win' side of the equation." Bush, he said, has been very careful to argue that if America goes to war, it will go all out to win.

The upshot is that while a majority is willing to support war to resolve the gulf crisis, there is not what might be called an invincible consensus. This is why Bush's window to war may shut very quickly.

In fact, Mueller notes that current levels of support appear significantly below initial public backing for both the Korea and Vietnam wars, even if the basic structure of opinion is similar. And, in making his case to the public, Bush has often been his own worst enemy. A State Department analysis of public opinion on the gulf attributes part of the decline in approval for Bush's handling of the gulf crisis to what it delicately referred to as an "increasingly critical response to changing policy explanations" by the president.

As noted in the State Department study, a CBS-New York Times survey in mid-August found that a 60-to-34 percent majority believed the president "has explained the situation in the Middle East well enough so that you feel you understand why the United States is sending troops to Saudi Arabia." By mid-November, the numbers had flipped: Only 41 percent thought the president had explained the situation well; 51 thought he hadn't. Bush may be doing a better job -- the latest polls show about half now say he's making his case adequately.

Bush's relatively low numbers are especially surprising because Americans are receptive to a variety of arguments for his policy. A Gallup survey for Newsweek conducted two weeks ago asked people to indicate whether they thought each of a list of reasons was or was not "a good reason for the U.S. to go to war against Iraq." The answers went like this:

57 percent said war would be justified to prevent Iraq from ultimately attacking Israel.

60 percent said restoring the former Kuwaiti goverment was a good enough reason for war with Iraq, up from 53 percent in a survey one month earlier.

60 percent said preventing Iraq from controlling a larger share of Mideast oil and threatening the U.S. economy was a good reason.

78 percent agreed that preventing Saddam Hussein from threatening the area with chemical and biological weapons was a good reason and 70 percent said preventing Saddam from developing nuclear weapons was an acceptable reason for war.

Only one reason failed to get majority support: Just 31 percent said "to lower oil prices" was a good enough reason to make war with Iraq -- one reason why you've heard so little lately from official circles about the oil rationale.

Polling questions like this have their dangers. Respondents offered a long list often like to say they agree with at least something on it -- to make the poll-taker happy, to demonstrate that they know what they're talking about or to sound open-minded. Such lists are thus better tests of which arguments the public finds plausible than measures of deeply-held convictions.

Moreover, questions about Saddam's nuclear and chemical weapons capabilities may elicit answers reflecting more the average citizen's fear of horrible weapons than attitudes toward Iraq and war.

Still, the poll found 92 percent of Americans thought at least one reason for war was good enough. And more than half of those questioned said at least four listed reasons were good enough to justify war.

Such findings ought to bolster the Bush administration's efforts to get Saddam to back down by making the war threat credible. But they invite a question which policy analysts, not pollsters, have to answer: Is the "quick victory" scenario plausible?

Just last week, the deputy commander of the U.S. forces in Saudi Arabia, Lt. Gen. Calvin A. H. Waller, warned that his troops "will not be ready for combat activities" on Jan 15. Such candor, assuming that's what it was, may be far more damaging to the president's cause than anything uttered by anti-war members of Congress. The public's backing for the war option depends heavily on its faith that the country really could win, could do so quickly and then get out. If the military seems to be questioning this rosy scenario, citizens are unlikely to believe politicians' claims to the contrary. Paradoxically, then, the greatest source of hope for opponents of American military intervention against Iraq may be military doubts, not moral qualms.

For on the basic issues raised by Iraq's invasion of Kuwait -- call them moral issues, if you will -- the president currently occupies the high ground in public opinion. To sustain that support, he needs to prove that he has a plausible strategy for success. With apologies to Michael Dukakis's speechwriters, the issue with Iraq really will come down to competence, not ideology.

Richard Morin is director of polling, and E.J. Dionne covers politics for The Washington Post.