WASHINGTON — There are enormous differences between the war in Iraq and the one in Vietnam that defined a generation. The current conflict hasn't lasted as long, taken nearly as many American lives or sparked the sort of anti-war movement that marked the '60s and '70s.

But when it comes to public opinion, Americans' attitudes toward Iraq and the course ahead are strikingly similar to public attitudes toward Vietnam in the summer of 1970, a pivotal year in that conflict and a time of enormous domestic unrest.

Some political scientists and historians predict that the Iraq conflict, like the one in Vietnam, will shape American attitudes on foreign policy and the use of military force long after it's over.

"This war is probably a really big deal historically in terms of America's perspective on the world," says John Mueller, a political scientist at Ohio State University. "What you're going to get after this is 'We don't want to do that again — No more Iraqs' just as after Vietnam the syndrome was 'No more Vietnams.' "

In a USA TODAY/CNN/Gallup Poll taken Friday through Sunday, more than half of those surveyed wanted to withdraw U.S. troops from Iraq within the next 12 months. In 1970, roughly half of those surveyed wanted to withdraw U.S. troops from Vietnam within 12 months. (Related: Poll results)

In both surveys, about one-third supported withdrawing troops over as many years as needed, and about one in 10 wanted to send more troops.

Arizona Sen. John McCain, a Republican, rejects any comparison with the Vietnam era.

"I wasn't in the United States in 1970," says McCain, a POW in Vietnam at the time. "But I am very aware of what happened in 1970. There's not massive demonstrations in the streets (now). There's not the kind of opposition — draft-card burning and all of that — (seen) during the height of the anti-war movement."

Still, McCain says he is "very worried" about polls showing waning support for the war. "I would not try to sugarcoat it. Some things need to be done better," he says.

Growing unease over the war in Iraq has been reflected in recent days on Capitol Hill, at the Pentagon and in foreign capitals.

In the Senate on Tuesday, Republicans defeated a Democratic proposal that called on Bush to outline a timetable for the phased withdrawal of U.S. troops. Republican leaders countered with their own non-binding resolution that urged next year "should be a period of significant transition to full Iraqi sovereignty."

"There's a growing desire to get out of Iraq, almost regardless of the consequences," says George Herring, a history professor emeritus at the University of Kentucky and author of America's Longest War: The United States and Vietnam, 1950-1975. "This is the way things began to develop in Vietnam after the fall of 1967."

In 1970, 56% said the decision to send troops to Vietnam was a mistake. (That number reached a high of 61% before direct American involvement in the war ended in 1973.) Now, 54% say the decision to send troops to Iraq was a mistake.

Split over war emerges in GOP

Declining support has its own consequences for Bush, making it harder for him to maintain party unity behind his policy, especially as the 2006 congressional elections approach.

"Politicians get twitchy when the poll numbers shift," says John Pitney, a former House Republican staffer and political scientist at Claremont-McKenna College in Claremont, Calif.

"The No. 1 instinct in politics is survival," says Andrew Kohut, director of the non-partisan Pew Research Center. With sagging approval ratings for Bush and for his handling of Iraq, the president is "going to have a much harder time than he's had so far in ... keeping people close to him," Kohut says.

Opposition to the war crosses party lines.

In the latest USA TODAY poll, a record 60% of those surveyed, including one in four Republicans, said the war wasn't "worth it." One in five Republicans said the invasion of Iraq was "a mistake."

Among independents, 60% called the war a mistake; 85% of Democrats agreed. There was no gender gap on the issue — that is, no difference in the opinions of men and women — but there was a racial divide. Half of whites saw the war as a mistake. Among blacks, that view was almost universal, held by 95%.

Concern over the course and costs of the Iraq war has become a major factor in unease about the direction of the country generally. In January, a 58% majority said things were going well for the United States. By this month, only 49% said things were going well.

Most of those who say things are going well in the country support the war. Most who say things are going badly — 50% of those polled — call it a mistake.

Bush has begun pushing back harder against critics, particularly Democrats who accuse administration officials of distorting or withholding intelligence when they were making the case to invade Iraq three years ago.

Speaking to troops at Elmendorf Air Force Base in Alaska late Monday, on his way to Asia for an eight-day trip, Bush said Democrats were "playing politics with this issue, and they are sending mixed signals to our troops and the enemy." He warned: "That is irresponsible."

At the Pentagon on Tuesday, Secretary of Defense Donald Rumsfeld acknowledged that many Americans want to know when U.S. troops can come home. He argued it would be a mistake to leave prematurely. "We must be careful not to give terrorists the false hope that if they can simply hold on long enough, they can outlast us," Rumsfeld said.

But Mueller says his study of wartime public opinion raises doubts about whether rhetoric can rebuild lost support for the war. "If history is any indication, there is little the Bush administration can do to reverse this decline," he wrote in an article in the current issue of Foreign Affairs magazine.

Mueller found parallels in the course of public opinion toward the wars in Korea, Vietnam and Iraq: Broad enthusiasm at the outset that declined steeply at first, then eroded slowly.

Casualties rise, support falls

In Vietnam and Iraq, some of the reasons given for going to war were undercut over time. For Iraq, that includes the failure after the invasion to find weapons of mass destruction or clear, prewar ties to the al-Qaeda terrorist network. Then, as casualties mounted, support for both wars fell.

"It's a basic cost-benefit analysis," Mueller says. As casualties rise, fewer people think the cause is worth the cost. After that, good news — for instance, a successful election or the passage of a constitution — can briefly boost support. But it typically dissipates.

"You can bring them back, but the question is bringing them back permanently," he says, "and that seems unlikely."

There are, of course, major differences between Vietnam and Iraq, including less tolerance for U.S. casualties.

More than twice as many U.S. troops were deployed to Vietnam in 1970 — 334,600 — than the approximately 160,000 U.S. troops now in Iraq. The death toll for American troops in Iraq passed 2,000 last month. In Vietnam, where U.S. involvement began on a small scale in the 1950s, nearly 54,000 U.S. troops had been killed by the end of 1970.

A majority of Americans began calling the war a mistake after the Tet offensive in 1968 — three years after the major build-up of U.S. troops there. By 1970, the Nixon administration had taken steps to reduce U.S. troop levels and casualty rates.

But the U.S. invasion of Cambodia in April 1970 created a firestorm. In May, four anti-war protesters were shot and killed by Ohio National Guard troops at Kent State University.

That furor prompted the first major challenge by Congress to President Nixon's leadership on the war.

In the Senate, Democrats proposed the Cooper-Church amendment, the first measure to limit presidential powers during wartime. It barred U.S. combat operations in Cambodia and Laos. After months of debate, it finally was passed in December.

"That's a pretty pivotal period in the war," Herring says.

Sen. Chuck Hagel, R-Neb., a member of the Foreign Relations Committee and a Vietnam veteran, said Tuesday's action in the Senate would be seen as a watershed in this war.

"People will look back on this day and say it was a turning point," Hagel told reporters after a speech at the Council on Foreign Relations — the point when Congress began to pressure the administration to lay out its exit strategy for Iraq.

Meanwhile, in Britain, the chief U.S. ally in Iraq, government leaders began suggesting this week that British troops might begin leaving Iraq next year.

British Prime Minister Tony Blair, who has been targeted by anti-war protesters himself, said on Monday that it was "entirely reasonable" to "talk about the possibility" that British troops could begin leaving Iraq by the end of 2006.

That discussion, he added, "has got to be always conditioned by the fact that we withdraw when the job is done."

Contributing: Oren Dorell, Dave Moniz, Barbara Slavin, Andrea Stone, wire reports

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