Media attention focused on the death of the 2,000th American soldier in Iraq last week. But that grim event alone probably won't prove a tipping point in public opposition to the war.
After 30 months of fighting, most Americans have already turned against the war. Polls find that 54 percent believe the United States made a mistake in sending troops to Iraq, up from 24 percent in March 2003.
It's not the specific number of casualties so much as the steady drumbeat of carnage that causes people to lose their stomach for war. The truth is that even dramatic events do not necessarily greatly affect support for the cause.
Compare Iraq to Vietnam. Although the 1968 Tet offensive, in which the US military took heavy losses, did cause people to worry that the war was not going well, support did not plummet. It simply continued to drift downward. In Iraq, support bumped up a bit when Saddam Hussein was captured and when elections were held, and it slumped at the time of the Abu Ghraib disclosures. But in each of these cases, it soon returned to its previous course.
What's unprecedented about this war is how fast support is eroding. Casualty tolerance in Iraq is clearly much lower than it was in Vietnam.
Using comparable poll questions, support levels for this war when 2,000 American soldiers have been killed are about the same as they were in the Vietnam War when well over 20,000 perished. This strongly suggests that the public places a much lower value on the stakes in Iraq than it did in Vietnam.
The erosion of support for the Iraq war has continued throughout 2005, with some fluctuations. Support for the war rose briefly at the time of the London bombings in the summer. But the attacks also tended to undercut the Bush administration's argument that the terrorists were so busy in Iraq that they couldn't operate elsewhere.
The Bush administration hopes to reverse the downward trend with upbeat speechmaking that claims progress in Iraq. The same approach was used in the Vietnam War but with little success. The problem is that people who always believed the war wasn't "worth it" won't be converted, and those who have become disenchanted are not easily won back. If you find you have bought a car for twice its value, you are likely to continue to regard the deal as a bad one even if you come to like the car.
Opposition to the war in Iraq is not just widespread, it's quite intense. More than 80 percent of war opponents say they "strongly" object, and more than half say they are angry about the war, not merely dissatisfied.
In addition, extensive comparative analysis by Gary Jacobson of the University of California, San Diego, has demonstrated that partisan divisions over not just this president but over this war are greater than for any president or any military conflict in the past half-century.
This means that approval levels for George W. Bush and his war depend mainly on the steadfast support of Republicans. The Democrats have become almost completely disaffected. Moreover, there are signs over the past month or two that support even from the remarkably loyal Republicans may be beginning to fade.
Polls, however, are not referendums. Eroding public support cannot keep the administration from continuing to prosecute the war any more than discontent did in Vietnam, unless it is expressed in congressional action. Moreover, though a decline in American casualty rates is unlikely to boost support, it may, as in Vietnam, cause the public to pay less attention to the conflict.
However, in one important respect, withdrawal from Vietnam was much more difficult politically for congressional opponents than it would be in the case of Iraq. North Vietnam held about 500 Americans prisoner, and leaving Vietnam without getting those prisoners back was a political nonstarter.
There is no comparable POW problem in Iraq - but that doesn't mean ending the war will be easy.
• John Mueller, professor of political science at Ohio State University, is the author of "War, Presidents and Public Opinion." ©2005 Los Angeles Times Syndicate.