Presidents fall into second-term slumps for different reasons. More important for President Bush is how they get out of them. Roosevelt gained an unprecedented third term by convincing the country that he alone was equipped to shield them against the growing threats from Hitler and the imperial Japanese. Ronald Reagan shook off the albatross of Iran-contra by joining Mikhail Gorbachev to wind down the cold war. Straining to survive the Monica Lewinsky mess, Bill Clinton boasted that he was responsible for the longest economic expansion in American history. ("Dow Jones, not Paula Jones.")

If a majority of the public thought the Iraq war were going well, Bush might naturally turn—as second-term presidents often do—to foreign affairs, climbing aboard Air Force One to pursue his aim of expanding democracy throughout the Middle East and the world.

During his last 18 months in office, Eisenhower flew to Asia, Europe and Latin America and deployed his war hero's popularity to seek new friends for America while trying to improve relations with Moscow. By the time Ike left office, most Americans had forgotten their anger over losing the space race to the Soviets.

Truman and Johnson would have loved to use foreign policy to boost their sagging popularity. LBJ was privately desperate to make the first presidential trip to the Soviet Union (even after Nixon's election to succeed him) and show Americans once and for all that he was no warmonger.

But as their second terms ground to a close, Truman and Johnson both sadly realized that the public was focused on the news from the battlefront. And so long as these beleaguered war presidents remained in office, that news never got better.

Historians sometimes view presidents very differently from the way the public did at the time. Sometimes they don't. Hoping for vindication by history, Nixon told Oxford students in 1978, after Watergate drove him out of office, "Let's get on to my achievements. You'll be here in the year 2000 and we'll see how I'm regarded then." As it turned out, not as warmly as Nixon had anticipated.

But in contrast, with a half century's hindsight, most historians consider Harry Truman one of the near greats. That would have surprised almost everybody but Mrs. Truman in March 1952, when her husband's Gallup poll approval rating was 25 percent.