Washington ? It’s no mystery why President Bush and his campaign aides have fought so hard to establish the legitimacy of their TV ad that includes scenes from the 9-11 attack on the World Trade Center.

When the commercial came under criticism from survivors of some of those killed by the terrorists and also from some members of the firefighters’ union, Republicans rushed to insist that the visual references were well-justified by the significance of that day for the country — and for the Bush presidency.

The importance of their defending that proposition was amply demonstrated by the Washington Post-ABC News poll released earlier this week.

Amid almost a dozen topics on which Bush had anemic and mostly negative ratings, one strong positive approval score stood out. By a margin of 63 percent to 34 percent, those surveyed applaud his handling of the campaign against terrorism.

Much of that approval goes back to the stalwart performance from the president in the first 10 days after the terrorists struck New York and Washington.

When the country really needed a president, he was there; his words and his actions serving as the rallying point for a shaken nation.

It is no wonder he wants to recall the emotions of the time; it was, in Churchill’s phrase, his “finest hour.”

But is it, as supporters of John Kerry and other critics suggest, wrong for Republicans to convert the emotions of that national tragedy into grist for a political campaign?

To answer that question, I went back, with help from Washington Post researcher Brian Faler, to 1944, when Franklin D. Roosevelt, almost three years after Pearl Harbor, was running for re-election.

What you learn from such an exercise is that Bush is a piker compared to FDR when it comes to wrapping himself in the mantle of commander in chief.

Item: FDR did not go to the Democratic convention in Chicago that nominated him for a fourth term.

A few days before it opened, he sent a letter to the chairman of the Democratic Party explaining his availability. And what an explanation!

“All that is within me cries out to go back to my home on the Hudson River, to avoid public responsibilities and to avoid also the publicity which in our democracy follows every step of the nation’s chief executive.”

But, he wrote, “every one of our sons serving in this war has officers from whom he takes his orders. Such officers have superior officers. The President is the Commander in Chief, and he, too, has his superior officer — the people of the United States. … If the people command me to continue in this office and in this war, I have as little right to withdraw as the soldier has to leave his post in the line.”

Item: Roosevelt delivered his acceptance speech to the convention by radio from where? From the San Diego Naval Station, because, he said, “The war waits for no elections. Decisions must be made, plans must be laid, strategy must be carried out.”

Item: If FDR’s politicizing of his wartime role seems blatant, what does one say of the main speakers at the convention?

Keynoter Robert Kerr, then governor of Oklahoma, declared that “the Republican Party … had no program, in the dangerous years preceding Pearl Harbor, to prevent war or to meet it if it came. Most of the Republican members of the national Congress fought every constructive move designed to prepare our country in case of war.”

So much for bipartisanship!

Item: Kerr was restraint personified compared to the convention’s permanent chairman, Sen. Samuel Jackson of Indiana. As he contemplated the possibility of a Republican victory, he was moved to ask:

“How many battleships would a Democratic defeat be worth to Tojo? How many Nazi legions would it be worth to Hitler? … We must not allow the American ballot box to be made Hitler’s secret weapon.”

If you accept President Bush’s premise that this nation is at war with terrorism, then you have to applaud the restraint his campaign has shown so far in exploiting the attack that began that war.

Far better than criticizing his ads, ask why Bush is not calling on comfortable Americans to make any sacrifices for the war effort and why he refuses to raise the revenues to pay for what he calls a life-and-death struggle.

Those are the legitimate issues.

David Broder is a columnist for Washington Post Writers Group.