The biggest unknown factor in the presidential campaign is whether there will be a major domestic terrorist incident before Election Day.
The key question is not just whether al-Qaida will seek to influence U.S. voting, as it did in Spain last March by detonating 10 bombs on three crowded Madrid commuter trains and killing almost 200 people a few days before national elections.
It is al-Qaida's mind-set: Do its leaders see their task as easier with President Bush or John Kerry in the White House? Or, from its warped perspective, is there no difference between the two men?
If al-Qaida prefers one candidate to the other, does it think it can influence the result to suit its ends?
Or, do the terrorists think their interests are better served by shelving any efforts within the United States before Election Day because an attack might benefit Bush?
After all, the assumption has long been that following Sept. 11, al-Qaida is planning additional attacks.
The whole idea of trying to figure out al-Qaida's mentality is obviously conjecture, but any notion that a terrorist attack within U.S. borders before Nov. 2 would not play a role in deciding the presidency is either naive or disingenuous.
Elections are the ultimate zero-sum game; what helps one candidate hurts the other.
And the actual truth of who would politically benefit in case of an attack may be less important than al-Qaida's view of the matter. Its judgment likely would guide the terrorists' decision on whether they should try to scare American voters into backing off the war on terror, which would presumably be their intent.
That calculation depends on whether the bad guys think U.S. voters would react as did their Spanish counterparts, or they agree with the conventional wisdom that such an attack here would just cement support for the war on terrorism.
The party of Spanish Prime Minister Jose Maria Aznar, a strong U.S. ally whose troops were part of the U.S.-led war in Iraq, had been strongly favored to maintain power but was defeated in the days after the bombings. Opposition leader Jose Luis Rodriguez Zapatero had pledged to pull out Spanish troops and did so upon taking office.
Bush has made clear that he won't be pressured into leaving Iraq any sooner than he deems necessary to put that nation on a course to democracy. Kerry, on the other hand, has offered seemingly contradictory policy statements, but in general he appears more willing to bring U.S. troops home sooner rather than later.
Suggesting that al-Qaida might prefer Kerry in the Oval Office will certainly enrage some, but rational analysis supports that view.
Although presumably the terrorists think that they were able to influence the Spanish election in a satisfactory manner, a key question is whether they believe the American people would react similarly.
In other words, would an attack spook U.S. voters into sweeping the "peace" candidate into office, or would it just stiffen the electorate's resolve to stay the course in a demonstration of national unity?
Unknown is whether the terrorists understand the American people well enough to make a correct decision that incorporates the prevailing wisdom on the subject.
The Spanish public, to put it bluntly, caved to al-Qaida.
Much has been written about the fundamental differences between the American and European mentalities. There are many, myself included, who think that this dynamic would lead to a much different U.S. public reaction to a pre-election attack than occurred in Spain.
If the terrorists attacked in this country before Election Day, the public reactions following 9-11 and Pearl Harbor suggest the president would benefit politically from an energized, united front against a common enemy.
Obviously, the circumstances surrounding any terrorist incident would be paramount in the public's electoral reaction. If voters judged that such an attack was made possible by Bush administration incompetence, Kerry might benefit.
Democrats, of course, may argue that voters will punish Bush if terrorists attack within the United States, and they may be correct.
But the evidence makes it difficult to see how an attack would be more likely to help Kerry than hurt him.
Of course, no American wants terrorism.
The decision about whether there will be an attack, however, rests in the hands of the bad guys.
If they can't be stopped, their timing is likely to be determined by their preference about whether they would rather fight an America led by John Kerry or George Bush.
Peter A. Brown is an editorial page columnist for the Orlando Sentinel.