Being among the minority of Americans who take a favorable view of the job President Bush is doing, we are often asked by members of the majority how to account for the president’s dismal job approval ratings. It’s a reasonable question — if the economy is humming along as well as it is and if Mr. Bush has succeeded in protecting Americans from a terrorist attack on the homeland since September 11, 2001, or, arguably, since the anthrax attacks that followed shortly thereafter, why is Mr. Bush doing so badly in the polls? Do Mr. Bush’s low job-approval ratings mean the Republicans have no chance of capturing the White House in 2008 or that they can only do so by running away from Mr. Bush and his policies?

The answer starts with the realization that Mr. Bush isn’t doing as badly in the polls as is widely assumed. Take the USA Today/Gallup poll of last week that found Mr. Bush with a 38% job approval rating. It sounds low — until you realize that the same poll found that congressional leaders — that is Democrats such as Senate Majority Leader Reid and Speaker Nancy Pelosi of Damascus — had a job approval rating of just 33%, lower than Mr. Bush’s. Other recent polls reported by RealClearPolitics.com consistently find the congressional leadership with lower approval ratings than Mr. Bush. Then realize that the USA/Gallup poll was of “adults,” as opposed to likely voters or registered voters. Screening for those qualities tends to tilt poll results by at least a few percentage points in Mr. Bush’s favor, or generically in favor of more conservative candidates, as the voting population is in general more conservative than the entire American population.

What’s more, job-approval ratings measure the performance of the president against some hypothetical ideal of a perfect president. Actual elections measure something different — voters’ preference between two less-than-perfect alternatives. In 2004, for example, voters weren’t asked whether they felt favorably about Mr. Bush. They were asked whether, given the choice between him and Michael Dukakis’s lieutenant governor (who voted for the Iraq war but against the $87 billion to fund the troops and who explained it by saying he voted for the $87 billion before he voted against it), they would choose Mr. Bush or Senator Kerry.

The 2008 election is shaping up similarly — it isn’t necessarily going to be a referendum on Mr. Bush, but a question about whether voters will prefer Mayor Giuliani or Mayor Bloomberg or Governor Romney or Senator Clinton or Senator Obama or some other candidate in the White House. It will be, in other words, a choice that pits mortals against mortals rather than a mortal against some platonic ideal of presidential perfection.

The objection will be raised that some of Mr. Bush’s predecessors had higher approval ratings and that Mr. Bush’s own ratings were sharply higher at other points of his presidency. Here we’d concede that part of the problem has been substantive, concerning Mr. Bush’s failure to win congressional approval of his campaign promises in terms of tax simplification, Social Security privatization, and immigration liberalization. As well as a failure to press the victory in the war on terrorism all the way to Tehran and Damascus. But we wouldn’t be too hard on the president. The article in USA Today that noted Mr. Bush’s latest low approval ratings reported, “Since the advent of modern polling, only two presidents have suffered longer strings of such low ratings. One was Harry Truman.” Since then Truman’s record has been acquitted quite well by something with a longer view than polls — history.