WASHINGTON Wars can help presidents get re-elected or drive them from office.
World War II helped land Franklin D. Roosevelt an unprecedented fourth term in 1944.
A deteriorating Korean War compelled Harry Truman not to seek re-election in 1952. An increasingly unpopular Vietnam War did the same for Lyndon Johnson in 1968.
Pundits say the jury is out on how President Bush's war both in Iraq and the broader one against global terrorism will play out politically in November. It depends on what happens on the ground between now and the election, most agree.
But history may offer some guidance.
''We're seeing a volatile war situation which could either make or break this president, depending not on what he says but what actually happens in the war,'' said Allan J. Lichtman, a history professor at American University. ''And everything is relevant, including these revelations of prison abuse.''
The international outcry over the mistreatment and humiliation of Iraqi prisoners by U.S. forces drew a rare apology last week from Bush as he stood alongside the king of Jordan in the White House Rose Garden.
Lichtman draws a parallel with the summer of 1864. The Civil War was not going well for the war-weary North. President Abraham Lincoln, under heavy political criticism, feared he would lose his bid for re-election. It took battlefield victories in the fall to turn things around for Lincoln, Lichtman said.
Bush has made his performance as a wartime president a main campaign theme. But six months before Election Day, Americans are expressing doubts about his Iraq policy. His approval ratings are slumping as violence in Iraq escalates and the prison abuse scandal is playing out.
Polls show that Bush continues to hold an advantage, though declining, over Democratic rival John Kerry on foreign policy and terrorism-related leadership.
''So long as the war in Iraq is seen as part of the war on terrorism, that definitely helps Bush,'' said pollster Andrew Kohut, director of the Pew Research Center in Washington.
National security crises can rally the public around a president.
Bush's approval ratings soared after the Sept. 11 attacks and got a smaller boost after the Iraq war began in March 2003.
Public sympathy, however, has its limits. Memories, too, can be short: Humiliation at Iran's prolonged holding of U.S. hostages contributed to Jimmy Carter's defeat in 1980.
While wars can drive up public approval ratings, such support can evaporate once the fighting has ended, as Bush's father found out. The elder Bush's surge in popularity from the 1991 Gulf War disappeared when the public lost confidence in the way he handled the slumping economy.
Woodrow Wilson enjoyed broad approval during World War I, a war he told Congress would make the world ''safe for democracy.'' Once the fighting was over, voters in the 1918 midterm elections rejected Wilson's appeal to return a Democratic majority to both the House and Senate.
Republicans won control of Congress and blocked Wilson's proposal for a League of Nations that was part of the 1919 Versailles peace agreement he helped negotiate in Paris.
Dwight Eisenhower used his extreme popularity as a World War II hero and a vague promise to end the fighting in Korea to propel himself into the Oval Office in 1952. Richard Nixon won re-election in 1972 after holding out the prospect of bringing a final end to U.S. involvement in Vietnam.
Ronald Reagan's performance as a Cold War commander and a defense buildup that helped speed the demise of the Soviet Union contributed to his 1984 re-election success.
Not all foreign policy fiascos have dire consequences for presidents.
After the mid-April 1961 collapse of the CIA-organized Bay of Pigs invasion of Cuba, President Kennedy declared that ''victory has a hundred fathers and defeat is an orphan'' and took responsibility for the botched attack.
Kennedy's popularity increased from a 73 percent approval rating in March 1961 to 83 percent in early May 1961, according to a Gallup poll.
That may show the value of taking responsibility, a lesson Bush and his advisers should heed, as Kerry and critics of the president have suggested. ''As president, I will not be the last to know what is going on in my command,'' Kerry said last week.
Some historians suggest Kennedy's rise in the polls probably had more to do with successful spin control. As Kennedy was taking public responsibility, his aides were busy circulating among reporters to privately blame Eisenhower for laying the groundwork for the ill-fated invasion.
Tom Raum has covered Washington for The Associated Press since 1973, including five presidencies.
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