In studying the mechanisms that determine how candidates prevail in presidential primaries, political scientists have often focused on momentum and how a candidate can pull away from the field. But they have also studied the “winnowing” process, analyzing the factors that cause candidates to drop out and, by attrition, ultimately leave one candidate as the nominee.
Four variables are the strongest predictors of success: (1) leading in fundraising; (2) leading the Gallup Polls prior to the election year; (3) winning Iowa; or (4) winning New Hampshire. All of the 11 eventual nominees led or prevailed in at least one of these areas.
Perhaps most obviously, winning one of the first two contests strongly correlated to longer durations: “Seven of the New Hampshire winners (Reagan, Carter, Bush in 1988 and 1992, Dukakis, Gore in 2000, and Kerry) captured the presidential nomination, while the remaining four (Hart, Tsongas, Buchanan in 1996 and McCain) mostly finished in second place overall. Six of the Iowa caucus winners ultimately secured their party’s nomination, but the other four did not.”
Moreover, the candidacy of the New Hampshire winner is 61% longer than a candidate receiving the average vote. “Iowa caucus results also matter, though the influence appears to be about half as great as that of the New Hampshire primary.”
“Pre-election year poll standings have a strong linear relationship with the success of candidacies.… The development of a popular following prior to the election year, during the ‘invisible primary’ stage, is an important determinant of presidential nominations.” Indeed, “Nine of the eleven nominees led the pack in campaign funds raised prior to the election year, and eight of the nominees led in the Gallup Polls.”
Those who have already held significant government positions — in Congress or state government — were more likely to drop out sooner, and their campaign’s average duration is 37% shorter than those candidates who have not held such offices. This is likely because they want to maintain standing in their party.
Over the period studied (1980 to 2004), there were no statistically significant differences in campaign duration times between Republicans and Democrats.
The study’s author concludes, “The new institutional equilibrium has undone one of the primary goals of the 1970s reformers — that of opening up the presidential nomination to a wider range of candidates. Traditionally strong candidates have adjusted their strategies to the new rules. Winning the presidential nomination is now most typically accomplished by establishing dominance in the pre-election phase and winning sufficient popular support in the initial contests to avoid being winnowed from the field.”