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Norpoth: New Hampshire's Crystal Ball in 2008

Topics: 2008 , New Hampshire , The 2008 Race

(Today's Guest Pollster contribution comes Professor Helmut Norpoth of Stony Brook University).

New Hampshire voters may mystify pollsters and pundits, but they have acquired an uncanny sense of picking candidates that go on to the White House. Whatever accounts for Hillary Clinton's surprising showing in her party's primary in New Hampshire, that victory makes her the best bet for Democrats to win the general election in November; likewise, John McCain's victory in the Republican primary in New Hampshire makes him the best hope for the GOP to retain the White House in November. These predictions are derived from a forecast model I developed that uses primary performance as the sole short-term predictor of the vote in the general election (the "Primary Model"). I have applied the model, with slight modifications, in the last three presidential elections, in which it correctly predicted the winners of the popular vote several months before Election Day. (See my 2004 paper in PS: Political Science & Politics). A race between the two New Hampshire winners, so the forecast, would be a nail-biter, with Clinton edging McCain by a margin of just a single percentage point of the two-party vote.

The use of primary elections to predict the outcome of the vote in the general election has some compelling advantages. One, it puts the estimation of a forecast model on a firm footing by letting us use elections all the way back to 1912, when presidential primaries were inaugurated. Two, it makes it possible to include both incumbent and opposition candidates in the model; granted, the incumbent candidate's performance may prove more powerful, but the effect of the out-party's primary showing is not negligible. And finally, the use of primaries as a predictor permits an unconditional forecast of the November vote at a very early moment. No ifs and buts. If one is willing to go with the outcome of the New Hampshire Primary, one can do it right now. The only uncertainty that remains is which of the match-ups will result from the nomination process. Chances are we may not have wait until the national conventions.

To measure primary performance in a standard format that allows for comparison across elections with varying numbers of candidates, I use an equivalent of the two-party vote in general elections. A candidate's primary showing is expressed as his or her vote relative to that of the winner (or in case of the winner in relation to the second strongest candidate). For incumbent-party candidates, the measure is adjusted, depending on whether they are sitting presidents or not. Moreover, the New Hampshire Primary is used only since 1952, when the state switched to a presidential-preference type of primary; prior to 1952, the model relies on the vote in all primaries.

Even though primary performance is the key, giving the model its name, the Primary Model also enlists a cyclical pattern of the presidential vote: the tenure of a party in the White House typically lasts between two to three terms. A compelling explanation for that dynamic is the term limit in presidential elections. Except for FDR, American presidents have eschewed running for more than two terms; and have been barred from doing so since then. The rule guarantees that incumbent presidents are missing from those contests in some periodic fashion, as is the case in 2008. In many such instances the absence of a sitting president with a high degree of popularity may improve the chances of the opposition party of capturing the White House. Given his high approval rating, Bill Clinton's ineligibility in 2000 probably hurt the Democratic prospects that year, although the absence of a much less popular George W. Bush in 2008 may be a blessing for the GOP. In any event, elections without a sitting president in the race tend to favor the opposition party more than elections with an incumbent running for another term. The Primary Model handles this dynamic by way of an autoregressive process (the presidential vote in the two previous general elections). In addition, given the use elections as far back as 1912, the model applies an adjustment for pre-1932 long-term partisanship.

From 1912 to 2004, the out-of-sample forecasts of the Primary Model pick the winner of the popular vote in 23 of the 23 elections, with 1960 being the only exception (and yes, that record includes Gore's popular vote win in 2004). The prediction equation for the presidential vote in 2008 (expressed as the Democratic share of the major-party vote) is:

.361 (RPRIM - 55.6) (-1) + .124 (DPRIM - 47.1) +.368 (VOTE04) -.383 (VOTE00) + 50.7 = .361 (RPRIM - 55.6) (-1) + .124 (DPRIM - 47.1) + 49.4

where RPRIM and DPRIM represent the primary support of the Republican (incumbent party) and Democratic (opposition party) nominees for President, capped within a 30-70 percent range, and Vote04 and Vote00 the Democratic vote shares in 2004 (48.8%) and 2000 (50.3%). The measure for the Republican candidate is inverted (-1) because the Democratic vote is used as the dependent variable. The formula produces the following forecasts of match-ups between the leading contenders in either parties (the vote for each match-up being the Democratic percentage of the two-party vote):

011508gpc.png

The PRIMARY MODEL predicts that in a race of New Hampshire Primary winners, Democrat Hillary Clinton would narrowly defeat Republican John McCain in the November general election (50.5 to 49.5 percent of the two-party vote). The predicted margin of victory, however, is so small that the confidence attached to this forecast is less than 60 percent, given the size of the forecast standard error (2.5). In match-ups between the Republican primary winner and Democratic primary losers, McCain would end up in a virtual tie with Barack Obama (49.9 to 50.1 percent) while defeating John Edwards (52.1 to 47.9 percent) by a margin close to one unit of the forecast standard error (2.6). At the same time, in match-ups between the Democratic primary winner and Republican primary losers, Clinton would dispatch Mitt Romney, Mike Huckabee, and Rudolph Giuliani by margins way beyond that error range. Finally, in match-ups between primary losers, both Obama and Edwards would beat any of the Republicans, and quite handily so in most cases.

That is no sign of partisan bias. Rather, it has to do with the Model assigning more weight to the primary performance of incumbent-party candidates than to the performance of out-party candidates. Nominating a primary loser, or even a candidate with a lackluster primary showing, costs the incumbent party more dearly than it does the out-party. Candidates not listed in the forecast table would do no better than the weakest one in their respective parties.

 

Comments

I've seen this analysis before, and it seems a bit far-fetched. First, we're dealing with a pretty small N, particularly if we accept that the modern primary system only begins in 1972. Second, New Hampshire only acquired its current role circa 1968 - maybe, and a better target year would be 1976. Third, the winner of the contested New Hampshire primary failed to win the nomination in 1984 (D), 1992 (D), 1996 (R)and 2000 (R), and a non-winner of NH won the presidency in 1992 (D) and 2000 (R). So I think that NH's power in predicting general election competitiveness is probably grossly overstated.

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Sarah:

Yes, I'm with arbistrista. Also, did you hold the other primaries (especially Iowa) constant?

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Jesse:

This doesn't even come close to making sense. The winners of the last five CONTESTED NH Primaries were: Tsongas '92, Buchanon '96, McCain and Gore '00, and Kerry '04.
NONE of them ended up as Presidents. To assume that elections 20 years old and older have equal or greater predictive ability on our current race than recent examples do is naive at best, and frankly I think nuts is a better description.

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Jeff:

Professor Norpoth's math is way over my head and I'm reluctant to pile on here on a matter where maybe I'm not even entitled to an opinion. He's a scholar and I'm not.
But I clicked through to his 2004 paper, written before the general election. His model forecast a Bush victory over Kerry 54.7% to 45.3%. The actual outcome was 50.7%/48.3%. His model also had Gore drawing 55% in 2000. Admittedly, he says he is using this model as a predictor of the winner and not the vote percent, but one question is whether the percent results should be considered "close enough" or perhaps a coincidence.
Like the previous commenters, I find it hard to dismiss the importance of variables that emerge after the NH primary -- the selection of a running mate, hostile coverage by the mainstream media, debate "gaffes" and campaign spending. Common sense tells you those factors, alone or in combination, can swing any close election.

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Another problem with this model: is there any reason to believe that the NH primary is a more effective predictor than any other state's primary? I would guess that states later in the process (such as SC and Ohio) nearly always predict their parties' nominee, while NH is far less succesful.

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Helmut Norpoth:

If any of you have seen this before, it's probably because you have heard of the Rule: since 1952 no one has won the presidency without winning his/her party's New Hampshire primary. Yes, one (clear) exception: 1992; the other (debatable): 2004--Gore loses White House, but wins popular vote. Which is the benchmark for election forecasting. Even the Iowa Market will pay out in that case, regardless of the electoral college. Anyone who thinks there is another state whose primary has a better track record, please find it.
Another thing to remember is the Primary Model does not simply use winning the primary as the predictor. For a sitting president that's not enough. You have to win above par for sitting presidents. So for Bush in 1992, who barely topped 50% in NH, the model predicts a poor day in November, even against a NH loser in the other party like Bill Clinton.
As for NH not being significant in the years before 1976, remember cases like 1952: NH launches Ike's presidential campaign and torpedoes Truman's. 1968: LBJ's lackluster showing against McCarthy casts a pall over his renomination and reelection. In those days, with only a dozen primaries, some of which did not offer candidate contests or were preempted by favorite sons, NH may have been more sgnificant than today.

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Anonymous:

Helmut knows his ****. That's all I'll say.

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