Those of us who are expecting some last minute drama to emerge from tonight's debate - the third act of what so far has been a relatively lacklustre piece of political theatre - will be sorely disappointed.
There will be no sharp quips or witty sound bytes that leave an indelible imprint on the memory of those who watch at home, or lofty ideas that seem to crystallize in front of our very eyes by virtue of their sheer simplicity and allure. The stilted and excruciatingly restrictive nature of America's presidential debates, combined with the tendency engrained in both candidates to frame and shape their arguments in a perambulatory and occasionally labyrinthine style of rhetoric, will take care of that.
Similarly, those hoping that McCain will somehow pull-out a final trump card, throw a political "Hail Mary" - or one of the plethora of other euphemisms typically employed by commentators in recent days to describe a man desperately searching for a way to postpone his slide into the political abyss - need to reconcile themselves with the cold, hard reality of this year's campaign.
John McCain lost this election a month ago, when he proclaimed that "the fundamentals of our economy are strong." John McCain lost this election in 2007, when he acknowledged that "the issue of economics is something that I've never really understood as well as I should." John McCain lost this election the minute he showed the slightest hint of ignorance regarding economics, by virtue of having the misfortune of being the Republican nominee for President of the United States during the most pronounced economic collapse to hit the Western world since the Great Depression, rather than in the midst of a foreign policy crisis.
John McCain lost this election the day he graduated from Annapolis and chose to become a naval aviator in the service of his country rather than an economist.
In a similarly fatalistic vein, tonight's debate will in its tragic predictability unfold along the following lines: Obama, too politically savvy to let the greatest of all the gifts slip from his grasp, will continue his recent policy of substituting lofty, illuminating and inspirational rhetoric for a cooler, more dispassionate mode of engagement that strikes just the right balance between detachment and aloofness.
McCain, for his part, will perpetuate his recent attacks on Obama's character but do so with an inquisitive rather than prosecutorial tone, mindful of the criticism levelled at his campaign in recent days for gleefully stirring the racial cauldron that continues to bubble in parts of 21st Century American society. Phrases like "Weather Underground" and "Rezko" will hang in the air, but sufficently open-ended in their presentation to allow the electorate to fill in the blanks.
The debate will be declared a draw by most; or spun as a marginal victory for the red or blue nominee, depending partly on the merit of the performances and largely on what outlet you get your news from; McCain will be judged to have done well, but not well enough; the polls will tighten, but only by a couple points; and millions of dollars will be spent between now and 4 November 4 in a vain attempt to stop the procession of history moving forward.
So why then does tonight's debate matter? Because on 4 November, after the confetti has fallen, and the lights have dimmed, and the last of the revellers have finally ceased their celebrations after partying into some godforsaken hour in the morning; after the cut and thrust of electoral politics has faded, Barack Obama will have to become President of the United States - not just president of those who voted for him.
The degree to which an Obama administration can successfully bring the country together, as he so often talks about, depends less on Obama himself and more, ironically, on McCain and the tenor and tone with which he chooses to run his campaign in the closing weeks of the election. Continue to stoke the fears and insecurities embedded in the psyche of many American citizens, as he has done (unwittingly or otherwise) in recent weeks, and McCain may create an ugly and vitriolic disconnect between certain segments of the electorate and its future president. Attempt to engage Obama substantively on the issues of the day, however unsuitable they may prove for gaining political traction, and the Arizona Senator may go some way towards restoring his reputation for character and integrity - a hallmark of his career prior to his campaign's assimilation by the Republic machine - and send a clear message to those who would preach a politics of ignorance and intolerance.
Tonight John McCain takes his first step in shaping his legacy for Barack Obama's America. That is why tonight's debate matters.