The Convention Bump

Abstract

Do the national conventions of the Democratic and Republican parties affect the poll standings of the presidential candidates they nominate? This study investigates whether these poll standings are bumped upwards following the party conventions. The convention bump is examined with Gallup and Harris time series data of presidential trial-heats throughout the course of seven campaigns from 1964 to 1988. We find that (1) with few exceptions, there is a convention bump;(2) the bump typically adds about 5 to 7 percentage points to the nominee's postoonvention poll standing; (3) the effects of conventions carry well into the general election campaign; (4) the first convention in the campaign sequence, held by the out-party, generates an additional but temporary increase in the nominee's support; and (5) convention bumps may be greater for harmonious conventions following divisive nomination contests.

The Timeline of Presidential Election Campaigns

“…The variance of e t would equal 0, and the polls would be represented by the constant term ␣ in equation 1. This expectation reflects the standard characterization of campaign effects, as is clear from existing literature that focuses on the effects of particular types of events (see, e.g., Campbell, Cherry, and Wink 1992;Geer 1988;Holbrook 1996;Lanoue 1991;Shaw 1999).…”

Issue and leader voting in U.S. presidential elections

“…A possible explanation for this result is the bump that candidates usually get from their conventions. Conventions tend to unite the party, create favorable media coverage, and thus increase people's enthusiasm for their party and candidate (Campbell et al, 1992). As a result, polls might have difficulties to accurately measure issue perceptions around conventions, since people might be strongly influenced by party identification.…”

When Have Presidential Campaigns Decided Election Outcomes?

“…Also, an analysis of correlations between the vote and various adjustments to the postconvention polls (adjusted by subtracting various percentages of the preceding bump) indicated that the correlation was highest between subtracting 30% to 40% of the prior convention bump. Although it would have been preferable to subtract a greater portion of the second convention bump because that had been more recent and presumably less of the temporary boost from that convention had dissipated, this was not possible because Gallup Polls prior to 1964 had not been conducted between the two conventions and thus the effects of the separate conventions could not be calculated for pre-1964 elections (Campbell, Cherry, & Wink, 1992).…”