Breaks of the Game: The Incumbency Rule in an Anti-Incumbent Year

By Christopher P. Borick

One of the most interesting phenomena of preelection polls in the United States is the way undecided voters break at the end of a campaign. Since the division of undecided voters on election day can determine which candidate prevails in a close election, it is surprising how little research has directly focused on this important question.

Perhaps the most widely accepted, if not empirically proven, theory regarding the impact of incumbency is that undecided voters behave differently when an incumbent is in a race. When an incumbent seeks reelection, voters are, in essence, asked to evaluate his or her record in office. As Guy Molyneux argues,

Elections are fundamentally a referendum on the incumbent. The first step in voters’ decision-making process is to answer the question “does he deserve re-election?” Undecided voters have basically answered that question in the negative, and their undecided status reflects the fact that they don’t know enough about the challenger (yet) to feel comfortable stating a public preference.

Theoretically, then, the incumbent is at a substantial disadvantage in securing undecided votes. Voters who are conflicted in the last days and hours before an election will be particularly hard for an incumbent to sway; thus, the “incumbent rule” holds that undecided voters will break for the challenger as the race draws to a close.

Followers of preelection polls often use the “incumbent rule” to help predict election outcomes. Press coverage regularly assumes that an incumbent with less than 50 percent support in the polls will be in jeopardy on election day. As undecided voters break to the challenger, incumbents will receive a portion of the vote that is at or below the level they received in the final election polls. This phenomenon seems to have been fairly well supported in recent presidential elections (see Table 1).     

While incumbents in presidential races do track close to their preelection poll numbers, we should be careful not to generalize to other races. Since the small number of cases and relatively high levels of turnout and public attention make presidential races exceptional in nature, it’s important to look at a wider range of elections to see how robust the incumbent rule may be. During the past two decades a number of studies have examined the way undecided voters break at the end of an election and the role that incumbency plays in these decisions.

The first study to examine the incumbent rule empirically was undertaken by Nick Panagakis in 1989. Panagakis examined 155 races, primarily from the mid- to late 1980s, to determine how undecided voters broke at the end of elections when an incumbent was present in the campaign. He found that in 127 out of the 155 cases in his sample, the challenger won a majority of the undecided voters. Conversely, there were only 19 races where the incumbent took most of the undecided voters (Table 2).   

Panagakis offered a number of explanations for his findings. He contended that

undecided voters are not literally undecided, not straddling the fence unable to make a choice—the traditional interpretation. An early decision to vote for the incumbent is easier because voters know incumbents best. It helps to think of undecided voters as undecided about the incumbent, as voters who question the incumbent’s performance in office.

In the Panagakis study the challengers who did not get a majority of the undecideds appear to be candidates who had held office of equal stature to the one they were seeking. Because voters were as familiar with the challengers as the incumbents, the challengers assumed the same characteristics as the incumbents, negating the advantages they otherwise would have had.