Sunshine Go Away Today, I Don't Feel Much Like Voting

In addition to what I think will prove to have been an underestimated swing of New Hampshire's unaffiliated voting bloc from John McCain to Barack Obama (an effect not captured in polls that have to make an assumption about the ratio of party identifiers to independents that will vote on each side of the aisle), there's another slightly abstruse variable that I think will help Mitt Romney to steal the win from McCain in New Hampshire today.

Given that McCain's average polling lead over Romney has dwindled to 3.6%, it looks to be a close matchup to begin with - one likely swayable by the conspiring of a few abstruse elements.

The lurking elements in this case are age and weather.  It's going to get close to 60 degrees in Concord today.  In a general election, good weather is good news for Democrats.  In an intraparty contest, it's good news for candidates whose support skews older, as elderly folks are more likely to make it out to the polls if the weather's accommodating.

[W]ith the temperature on primary day running some 20 degrees above normal, William Gardner, New Hampshire’s secretary of state, is predicting a record turnout of half a million voters. The pleasant weather may encourage more elderly people than usual to come out, he said.

According to the most recent WSJ/NBC poll (pdf), Romney's vote share among those over 65 (30%) is twice as large as his support among 18-34-year olds (15%) and 33% greater than his overall share (10%).  By comparison, McCain (whose support also skews older), enjoys a much smaller 33% premium among the 65+ segment over the 18-34-year olds and just 14% over the voting population on the whole.

Admittedly, that poll is a couple weeks old and it was national, not specific to New Hampshire.  But I can't think of a good reason to assume Romney's relative appeal among older voters should be significantly less than in other states (beyond whatever extent to which New Hampshire's fondness for Senator Septuagenarian draws on a strong sense of generational identification among seniors).

What's more, the state's age distribution (relative to the country at large) tends to amplify this effect.  While fraction of the population over 65 is nearly identical, the youth vote in New Hampshire (Obama rallies notwithstanding) is meaningfully smaller (18.5% in NH vs. 20.9% nationally, per Census data), meaning McCain's got more of his support wrapped up in the demographic that would turn out rain or shine, while Romney can expect an incremental boost if conditions are more accommodating than expected for voters who have a harder time getting around.

I don't know if there's data available that indicates just how much of an effect nice weather has on the turnout rates among the age segments (if anyone does, please advise), but in such a close race, a few nudges for either candidate could well make the difference.

Yesterday, I predicted Mitt would edge out McCain by 3 points in today's race and I continue be satisfied with that guess.  On the other side, however, I gave Obama only a 5-point margin.  It's looking more and more likely that he'll beat that spread.