The last national poll that showed Mr. McCain ahead came out Sept. 25 and the 232 polls since then have all shown Mr. Obama leading. Only one time in the past 14 presidential elections has a candidate won the popular vote and the Electoral College after trailing in the Gallup Poll the week before the election: Ronald Reagan in 1980.
But the question that matters is the margin. If Mr. McCain is down by 3%, his task is doable, if difficult. If he's down by 9%, his task is essentially impossible. In truth, however, no one knows for sure what kind of polling deficit is insurmountable or even which poll is correct. All of us should act with the proper understanding that nothing is yet decided.