Reality drives presidential approval. Much more than rhetoric, speech venues or staff shuffles, it is real events that determine a president’s public standing.

President Bush got to 90 percent approval not by dint of his hard work or winning personality. Despite White House claims, eagerly lapped up by commentators at the time, he had not forged a unique relationship with the American people, nor had the country undergone an ideological transformation.

Rather, Bush benefited from having been in office during the kind of events that normally move people to rally around their president. The unique intensity and character of Sept. 11 and the ensuing invasions of Afghanistan and Iraq created a much longer-lasting “rally effect,” but it was the nature of these events that drove the president’s popularity to new heights.

Today, a different set of realities have driven the president’s approval rating to historic lows. His failure in Iraq, his failure in dealing with Katrina and his failed efforts to deal with energy, gas prices and healthcare have all contributed to his misfortune.

But despite their great powers, even presidents are limited in their ability to alter reality; hence the air of deep disappointment engulfing the White House in the wake of the president’s immigration speech.

Only two policy levers under the president’s control had any chance of lifting those approval ratings. The first was sending troops to the border in an attempt to stem illegal immigration. Given public support for the idea and the drama of an Oval Office address announcing troop deployments, the White House had every reason to hope — and pray — this move would improve the president’s public image.

It has not. From the post-speech polls, it appears that Bush gained, at most, an extraordinarily modest three points, leaving him at 36 percent. Only Richard Nixon had approval ratings this low going into the summer before a midterm. (Of course, he resigned before the election and his party went on to lose 48 House seats.) They’ve taken one of their two best shots and it has not hit the mark.

Only one other action the president could take before November has any possibility of producing a meaningful upturn in Bush’s ratings — a major troop withdrawal from Iraq. Many have been speculating about this possibility for months. With the increasing violence there, from the perspective of the president’s policy arguments, a withdrawal seems even less likely than it did a few months ago. But the political dynamics may be more compelling than the policy ramifications.

The logic is simple, if cynical. No president with approval ratings under 50 percent has lost fewer than the 15 seats Democrats need to retake the House. A Democratic House would make life more difficult for the president by setting a different agenda, one more in tune with public preferences. The only way to raise those approval ratings and help prevent a Democratic takeover is to withdraw troops from Iraq. It is hard to imagine any other policy change or scheduled event in the next six months that is capable of producing a meaningful increase in the president’s ratings — which brings them back to withdrawal.

By telling candidates to run on Iraq, Karl Rove appears to be signaling that politics will determine the policy. It is inconceivable that he would urge Republicans to campaign on a war that most Americans have concluded was a mistake, unless there was something like a withdrawal up his sleeve.

However, the negligible response to the immigration speech suggests that it may be too late, that the image of failure attached to this president has become a reality of its own.

Mellman is president of The Mellman Group and has worked for Democratic candidates and causes since 1982, including Sen. John Kerry (D-Mass.) in 2004.