Candidate Support in Primaries

Ever since presidential primaries were introduced, in 1912, the ultimate nominees have played a key role in those contests. Only once (1920) did neither party give the presidential nomination to its primary winner.²

How primary support for a presidential nominee translates into general election support is best examined separately for the party with a president in the White House and the out-party. In the party holding the White House at the time of a presidential election, many of the nominees, of course, are presidents seeking reelection. Or they are incumbent vice presidents winning their party's nomination (Richard Nixon in 1960, George H. W. Bush in 1988, and Al Gore in 2000), turning the presidential contest into a “succession election” (Weisberg and Hill 2004). During the period of interest (1912–2000), it was quite rare for the incumbent party to nominate a presidential candidate lacking any official connection to the outgoing administration (Democrats in 1920 and 1952).

Until 1952, no single state with a primary could count on playing the lead role in the presidential-selection drama. That changed with swift and lasting impact when the state holding the first contest decided to put presidential candidates rather than convention delegates on the ballot. Since 1952, New Hampshire has allowed primary voters to check their preferences for would-be presidents rather than delegates. That switch “gave presidential hopefuls an opportunity to demonstrate early strength” (Buell 2000, 93), and they seized on it immediately. The beauty-contest format also propelled New Hampshire into the most coveted spot of the primary season, attracting more media attention than any other state (Adams 1987). To win in New Hampshire, however small and unrepresentative, meant a boost for a presidential hopeful that a victory in no other state could match since 1952. At the same time, many of the subsequent primaries have lacked competition, proving little about the electoral appeal of the leading candidate in the general election. So, beginning with 1952, only the vote in the New Hampshire primary will be used, whereas for elections from 1912 to 1948 the vote of all primaries is used.

Figure 1 plots the vote in the general election against primary support in the incumbent party. To establish a standard measure, the primary support of the nominee in each party is computed based on the sum total of votes received by that candidate and his chief primary rival (the one with the next most votes, or the leading vote-getter if the nominee did not win the primary battle). That rule will also be applied to primary contests of the opposition party, where it is actually far more compelling.

As for the vote in the general election, the share of the incumbent-party candidate is based on the major-party vote only; votes for third-party candidates are excluded.³

As shown by Figure 1, primary support offers a strong, though not perfect, predictor of electoral support for incumbent-party candidates in the general election. Any time primary support falls below 50% (by the standard measure adopted here), the presidential candidate of the party holding the White House loses in the general election (getting less than 50% of the major-party vote). The precedent was set by President William Howard Taft in 1912: he lost the primary battle and went on to lose the general election. By the same token, nearly every time primary support exceeds 50%, the candidate of the White House party goes on to victory in November. That precedent was set by President Woodrow Wilson in 1916: he won the primary battle and went on to win the general election. But there are exceptions to this rule. Several times an incumbent candidate was defeated in the general election despite winning most of the primary support. Case in point: President George H. W. Bush in 1992: ahead in the primary count, but behind in November of 1992. It appears that for sitting presidents 50% is not a safe mark. Significant opposition in the primaries hints at trouble for re-election. Yet regardless of whether or not a sitting president is running, incumbent-party candidates appear to gain little further in general-election safety once they reach about 75% of support in the primary battle. In other words, the predictive relationship between primary support and November vote is not linear, or is linear only within a restricted range of primary support. That is a point to consider for the estimation of the forecast model.

Turning to the primary battle within the out-party, Figure 2 suggests that the better the opposition-party candidate does in primaries, the worse the incumbent party fares in the November election. Primary success and general election victory go hand in hand for the out-party. That was the precedent set by Wilson in 1912. But it did not always hold. Most notably, it did not do so for Al Smith (1928) or Michael Dukakis (1988); but then in each of those instances the incumbent party had nominated its primary winner. By the same token, the electoral prospects for the out-party in November are gloomy when the primary support of its candidate falls short of 50%. In most of those elections, the incumbent party has won the general election. One exception is the 1920 election. The Democrats lost the White House in a landslide to a Republican candidate (Warren Harding) who barely registered in his party's primaries that year. As Figure 2 makes clear, the 1920 case is an outlier, but it is also the only outlier. Even in the old days—contrary to much conventional wisdom—winning general elections without strong primary support was not common. In sum, the predictive power of primary success for general election performance is impressive for the out-party, competing with that of the incumbent party in some cases and complementing it in others.

The Forecast Model

As before, the forecast model also enlists a cyclical dynamic of the presidential vote familiar to readers of PS (Norpoth 1995; 2001; also Midlarsky 1984). One explanation for that dynamic, as subsequent research has suggested, may be the existence of a term limit in presidential elections (Norpoth 2002). Except for Franklin Delano Roosevelt, 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, the latest instance being the 2000 election, when the two-term limit barred Bill Clinton from trying to keep the White House in Democratic hands. A second-order autoregressive process with a positive sign for the vote at lag one (the preceding presidential election) and a negative sign for the vote at lag two (the presidential election two terms back) captures that kind of periodicity.

The forecast model for 2004 also includes a new predictor that is nonetheless familiar to every student of elections: longterm partisanship (Campbell et al. 1960). The overall balance of party identification in the electorate creates a normal-vote baseline that remains stable over long stretches save for rare realignments. The stability of party identification lets many forecast models get away with ignoring this factor. But that is less defensible for one that covers elections as far back as 1912. There is no question that the basic party division of the American electorate has changed since then. The 1930s, by all accounts, witnessed a major realignment that requires an adjustment of the normal-vote baseline of partisan support. A time series analysis of the congressional vote from 1828 on, in presidential as well as midterm years, shows a long-term partisan shift from about 54–46 in favor of the Republican Party to 53–47 in favor of the Democratic Party during the 1930s (Norpoth and Rusk 2003). The forecast model incorporates this shift of the partisan baseline owing to the 1930s realignment.

The parameters of the model are statistically estimated with data from presidential elections since 1912. Note that the dependent variable is the Democratic percentage of the majorparty vote, regardless of whether that party was in the White House or not. As a result, the primary-support variables had to be inverted for elections with Republicans in control.⁴

The evidence in Table 1 confirms that all predictors prove significant. The effect of primary support for the incumbent-party candidate is enormous and far more significant than is the effect of primary support for the opposition-party candidate. Partisanship also exerts a powerful influence on the vote. The adjustment of the normal-vote baseline for the New Deal realignment pays off handsomely. So does, once again, the cyclical dynamic of presidential elections.

So what outcome does the model predict for the 2004 election? The key is the New Hampshire primary where George W. Bush took 87% against token opposition in the Republican race, while John Kerry beat his closest rival, Howard Dean, 59.3 to 40.7% of the Democratic vote for those two candidates.⁵

Along with the other predictors of the model, that leads to the forecast that Bush will defeat Kerry by 54.7 to 45.3% of the major-party vote.⁶

Given his victory in the Democratic primary in New Hampshire, Kerry nonetheless would do best among all possible Democratic contenders. For Bush to face defeat in November, his primary showing in New Hampshire would have had to be around 50%, as was the case with his father in 1992. With the Democratic nominee garnering around 60% (of the top 2 candidates), the forecast of the November vote in that case would be a Bush defeat. Kerry would beat Bush 53.3 to 46.7%. The forecast model is even-handed. It has no partisan favorite. All that matters in the short run is how the major-party candidates do in the primaries. It is true, though, that the showing of the in-party candidate matters far more than the showing of the out-party candidate.

How much confidence does this forecast of a Bush victory inspire? The estimate of the forecast error, given the model standard error and the values of the predictors, comes to 2.7. That would allow us to reject the hypothesis of Bush losing (falling below 50% of the major-party vote) at the .05 level. In other words, the forecast of a Bush victory over Kerry has a 95% certainty. The certainty of a Bush win over other Democratic nominees would be even higher.

How well has the model done in forecasting presidential elections so far? Earlier versions of this model predicted Democratic victories in 1996 and 2000. The forecast of the Clinton vote in 1996 (57.1%) was off by 2.4 points (in Campbell and Garand 1996, 8) whereas the Gore forecast in 2000 (55.0%) was off by 4.7 points (Norpoth 2001, 45). While in both cases the forecast model relied on the cyclical dynamic, primary support was handled differently than it was in the current model. For 2000, only incumbent-party support entered into the forecast and simply as win-lose dichotomy. That may have given Al Gore an undue boost in the November forecast. The current model with primary support measured as the relative vote share of the nominee comes very close to the 2000 result, as Table 2 shows, at least retroactively. All in all, these “in-sample” predictions (the fitted vote of elections included in the model estimation) point to the right winner in all but one election (1960), while getting Bush's victory in the electoral college right in 2000. In most elections, the prediction deviates from the outcome by no more than 2 points. Other than the 1960 contest, only the 1972 and 1964 elections produce large errors, which do not hurt much, however, since those outcomes were landslides.