Sometimes people (notably, but not always, Republicans) talk about an “enthusiasm gap” between the two parties like it’s some sort of a testament to the Truth of the Cause. It is actually, as Nate Silver reminds us again today, just a mechanical assessment of the propensity of registered voters from one party to vote as compared to the other. It’s not a whole lot of people, and much of the usual GOP advantage stems from fairly obvious socio-economic factors bolstered in the last few years by the extraordinary polarization of Americans by age (old folks at every place in every time since voting was invented vote in significantly higher numbers).
Enthusiasm gaps can also be increased, decreased or even erased by events, and that seems to be a large part of the story of Obama’s post-convention “bounce.” The “enthusiasm gap” (again, the gap between registered and likely voter margins) favoring Romney had been running at 3%, as compared to a historical average since 1988 of about one-and-a-half percent. Now it seems to have declined to the historical average, which means the impact of the convention had at least as much to do with base motivation as swing-voter persuasion (though probably owed something to both).
The key thing to understand is that there is nothing particularly mystical about “enthusiasm gaps” or their relative size or absence. It’s measurable. It operates in fairly predictable ways. And it has little or nothing to do with the subjective excitement levels of subgroups of voters. As I like to remind people, no matter how psyched you are to vote to cast the heathen from the temples of power, you only get to vote once, so unless your enthusiasm is communicable to others, it just doesn’t matter.
So if either side going into November 6 thinks it has some “secret” advantage thanks to enthusiasm, they are probably fooling themselves. Indeed, factors affecting last-minute turnout are far more likely to involve GOTV resources or (on the negative side) voter suppresion measures. And even those matter less than in the past (relatively speaking) before of the growing prevalence of early voting.
So even though this is indeed a “base” election more than is usually the case, there’s only so far enthusiasm can take you, and if it does, pollsters will probably notice it.