A recent piece from Dan McLaughlin at RedState was largely overlooked, but it is hugely important. McLaughlin went through the polls from RCP and constructed averages for mid- to late-September going back to 2002. What he found was a substantial amount of uncertainty between what polls showed in mid-September and the actual result. Yet there was order within that uncertainty. Seven races flipped leads in 2012, all toward Democrats; two flipped in 2010, one for each party; three flipped in 2008, all toward Democrats; three flipped in 2006, all toward Democrats; four flipped in 2004, all toward Republicans; and three flipped in 2002, all toward Republicans.
McLaughlin notes, correctly, that in these years, the races broke almost uniformly toward the “wave” party. But his point is merely that there is a bunch of uncertainty built into mid-September polling. Our question is a bit different. After all, we don’t yet know who the wave party is for 2014, if in fact there will be one. Let’s dig a bit deeper.
If we look closely at the data, there seems to be a “break point” in races where a candidates’ lead is five points or less. There are candidates who have led by more than that at this point but who went on to lose — Max Cleland in 2002, for one — but they are few and far between. On the other hand, candidates who have led by five points (rounded) or less have won only 15 of the 33 races in which they have been involved — about a 50-50 proposition. Of the 10 races listed above, only Minnesota shows a larger lead than five points.