How the Convention Ball Bounces

Forget the Olympics. Political junkies are in the convention pre-season. As we approach the Democratic National Convention on August 25 to 28 and the Republican National Convention on September 1 to 4, analysts just want to know one thing: How big are the bounces?

The "bounce", of course, refers to the jump in the polls that a party experiences as a result of its week of media propaganda, broadcast free on all major news networks and in every news publication. Don't get us wrong. We favor giving each party its chance to tell a story about its nominee and its principles; this is invaluable civic education for voters who don't pay close attention normally.

Yet we shouldn't see the conventions as more than they are. Ever since the 1972 GOP Convention that re-nominated President Richard Nixon, when the conclave literally followed a minute-by-minute script that detailed how long delegates should applaud in each instance, the parties have striven to follow the pure public relations model. Nary a discouraging word is spoken, every picture for the cameras is perfect, and "boring" becomes a religion.

Thus, at the end of the week, with the nominee having delivered a much practiced and poll-tested acceptance address and been accompanied by balloons, confetti, and family aplenty on stage, the candidate ought reasonably to be at his polling peak. The extra points added by the convention comprise the bounce, and size matters. The parties compare their bounces, and inevitably someone has a case of bounce envy.

Figure 1. REPUBLICAN AND DEMOCRATIC CONVENTION BOUNCES

In six of the 15 presidential elections since World War II, the overall third party vote has exceeded the Democratic or Republican margin of victory in the popular vote. Those half dozen elections are indicated below in BOLD. The number includes the trio of contests from 1992 through 2000, when none of the winners attained a majority of the popular vote.

Note: An asterisk (*) indicates that Ross Perot dropped out of the '92 race on on July 16, 1992. This impacted the polls following the Democratic National Convention which, ended on the same day, much more so than the GOP post-convention polls in August.

Source: Gallup polls from Roper Center's iPoll database.

Let's look at the record from 1960 to 2004 in the table above. Several observations can be made from these twenty-four conventions.

• Bounces are normal but not universal. In all twelve cases, the GOP nominee got a bounce, and the same was true in nine of twelve conventions for the Democrat. Lyndon Johnson had already peaked in 1964, at about the level of the vote he actually received on election day (61 percent), so no statistical change was seen from pre- to post-convention. George McGovern's disastrous convention in 1972, when internal disputes pushed his acceptance address into the wee hours on the East Coast, netted him a dead cat bounce. And John Kerry didn't budge, at least in the Gallup Poll, from the number 48 percent--precisely his proportion of the vote in November. Kerry had a high floor, due to opposition to George W. Bush, and a low ceiling as well, owing to Bush's strong base backing.

• The average size of a bounce has been 6.8 percent--slightly higher for Democrats (7.3 percent) than Republicans (6.4 percent).

• Despite the averages, there is considerable variance in the size of the bounce from election year to election year. Richard Nixon holds the record for best bounce on the GOP side (12 percent in 1960 and 11 percent in 1972), Bill Clinton grabbed the Democratic gold with a massive 28 percent in 1992, but this was due primarily to Ross Perot's decision to abandon his Independent bid at about the time of the Democratic convention. Perot thus indirectly encouraged his change-oriented voters to unite with the out-of-power Democrats to defeat Perot's real nemesis, President George H.W. Bush. (The mercurial Perot reentered the contest in early October 1992 and pulled a remarkable 19 percent in the actual election.)

• The size of the bounces can be deceptive in predicting the November winner and loser. Nixon's big 1960 bounce led to a loss, while his nearly equal 1972 bounce resulted in a landslide. Similarly, Jimmy Carter's 1976 bounce of 13 percent presaged his triumph, but his 12 percent gain in 1980 couldn't stop a landslide defeat. Also, George Bush's miniscule 2004 bounce of 2 percent didn't prevent his victory.

• Bounces can fade quickly. Historically, this has been truer on the Democratic side. Jimmy Carter slid from 63 percent after his convention to 51 percent on Election Day 1976, Michael Dukakis from 54 percent to 46 percent in 1988; and Bill Clinton from 59 percent to 43 percent in 1992.

• It doesn't make all that much difference which party has the first or second convention. Whatever the post-convention bounce numbers turn out to be after the second convention, the polls appear to revert to a reflection of the underlying conditions of the election year once a couple of weeks have passed. That is, when the election fundamentals are favorable to the White House party (good economy, peace, no big scandal, etc.), then the candidate of the White House party moves briskly into the lead, and the reverse is also true, of course.

• The actual standings of the candidates after both conventions are sometimes amazingly predictive of the November results--and other times are terribly misleading--meaning that we just can't rely on bounces to tell us all that much. The post-convention poll numbers for JFK in 1960, LBJ in 1964, Nixon in 1968, Carter in 1980, Reagan in 1984, Mondale in 1984, Dole in 1996, Bush in 2000, Gore in 2000, and Kerry in 2004 were reasonably close to the percentage they received on Election Day, and occasionally this particular number foretold their precise November vote proportion. But in the other fourteen cases, the post-convention number was misleading, marginally or grossly. Statistically, this makes the bounce meaningless in a predictive sense.

The last point is by far the most important. Recent history suggests that there is a better than even chance we'll be misled by the post-convention bounces in 2008. Yet forests will be lost to produce the newsprint for the stories about the overarching significance of 2008's post-convention bounces. And the "tubes" that comprise the internet (in the immortal description of now-indicted Alaska U.S. Sen. Ted Stevens) will be clogged with breathless analysis of the same numbers.

The Crystal Ball's readers are hereby forewarned. Pretty propaganda shows can move polls temporarily, but it is the election fundamentals that determine the general election outcome.

Larry J. Sabato is the director of the Center for Politics at the University of Virginia.

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Views expressed in this column are those of the author, not those of Rasmussen Reports.