But what if all other things aren't equal? What if the highly disciplined, basically one-issue campaign Republicans and their Tea Party allies have so assiduously run - namely, the promise to do a better job than the Democrats of creating jobs, keeping down spending and curbing the bloat in government - is up-ended by one or more terrorist attacks?

In such an event, there would, of course, be many other factors that would come into play before the electoral repercussions are considered.  These include: the death and destruction wrought by the perpetrators - especially if they are not merely jihadists operating commando-style in the mold of the perpetrators of the Mombai massacre, but attackers wielding weapons of mass destruction; the possibly widespread disruption of infrastructure and services, both governmental and those of the private sector; and the planning and execution of appropriate retaliation against the perpetrators and those who may have abetted the attacks, quite possibly at home as well as abroad.

Still, it is predictable that terrorists who undertake mass murder on the eve of an election in a democratic polity like ours both seek and will surely have an impact on the polls.  The question is:  With what effect?

Assuming the balloting could and would go forward across the country as scheduled, voters might be reinforced in their expected turn to the Republicans.  After all, the GOP has been seen as more robust on national security than the Democrats for a generation and much of the blame for our present vulnerability could rightly be laid at the feet of the Obama administration.

On the other hand, Americans tend to rally around the President in times of grave national crisis and war.  If Mr. Obama responded forcefully and effectively - a big if, but not out of the question - Republican prospects this Fall might be considerably different than they seem at the moment.  That is especially true insofar as the GOP has lately done little to differentiate its positions on national security from those of the Democrats; in fact, some prominent Republicans have taken to insisting that tens of billions of dollars must be cut from the defense budget in the months ahead.

Sadly, we may be about to find out which of these scenarios - or some other - eventuates.  Within the past few days, several ominous warnings have been received:  At the unrepentant Times Square bomber's sentencing hearing last week,  the defendant declared that the United States would be subjected to more murderous attacks like the one he attempted.  Informed sources report that U.S. intelligence believes teams of terrorists may now be at large not only in several European nations (for whom travel advisories were issued last week by the State Department), but here as well.

Then, we have just learned from the indispensable Middle East Media Research Institute (MEMRI) of a dramatic sea-change recently announced by the leader of the Muslim Brotherhood (MB).  As the Center for Security Policy's new Team B II report (ShariahtheThreat.com) documents, the MB has for years misleadingly encouraged Western non-Muslim audiences to believe that it is a non-violent organization. In fact, it would be more accurate to describe the Brotherhood (or Ikhwan) as "pre-violent."

While the MB espouses techniques associated with a stealthy or "civilization" jihad, these methods are to be employed to advance precisely the same goals as are espoused by al Qaeda and others who favor terrifying violence: the global triumph of the totalitarian program known as shariah under a single Islamic ruler (or Caliph).   And, more to the point, Brotherhood doctrine makes clear that seditious political influence operations and other non-violent methods are to be used only until the conditions are ripe to revert to violence.

It is, therefore, of extreme concern that the Ikhwan's international chief,  Supreme Guide Muhammad Badi, has lately called for his followers to adhere to "Allah's commandment to wage jihad for His sake with [their] money and [their] lives so that Allah's word will reign supreme" over all non-believers.  Badi's call to jihad can only make pre-election attacks more likely.

Taken together, indicators of an incipient threat to our homeland suggest that our enemies perceive President Obama, his administration and the nation as a whole to be increasingly submitting to shariah.   Until now, the principal enabler of such official behavior has been Homeland Security Advisor John Brennan with his "see-no-evil, speak-no-evil" approach to this threat. Mr. Obama's appointment last week of a wholly unqualified individual - Democratic lawyer and political operative Tom Donilon - as his National Security Advisor, can only intensify that perception, inviting the most grave of repercussions.

The possibility of imminent attacks from any shariah-adherent quarter should concentrate our minds.  Presumably, the Obama administration's conduct that has emboldened our enemies and that could create a politically dramatic "October Surprise" has not been intentionally pursued toward that end.  In any event, it now behooves all Americans - Republicans and Democrats alike - to get clear about the nature of the enemy, to stop its grand jihad and to work together to keep America shariah-free.

Frank J. Gaffney, Jr. is President of the Center for Security Policy, a columnist for the Washington Times and host of the nationally syndicated program "Secure Freedom Radio" heard in Washington at 9:00 p.m. weeknights on WTNT 570 AM.