This column was written by CBS News director of surveys Kathy Frankovic.
Will the party conventions have an impact on the presidential race? Historically, conventions can give a candidate a "bounce" or a "bump" in the polls, though sometimes it's just a slight one. How likely is that this year? Could it just be a lot of "noise?"
Polls have suggested - consistently -- that the race is fairly close, albeit with Democratin the lead. They also show many voters are undecided, or have not yet made a firm choice. In the , for example, completed earlier this month, 13 percent of registered voters were undecided and nearly three in ten of those with a choice said their minds could still change.
So there is definitely the possibility of movement in the next few weeks. But given their schedules, can we expect the conventions, on their own, to affect public opinion directly? This year, there will be only a three-day gap between the two conventions. The Democratic Convention ends on the Thursday night before Labor Day Weekend and the Republicans begin their convention on Labor Day itself. Will we even be able to measure whatever impact the Democratic Convention has on Obama before it's time to measure the GOP convention's impact on? And will we be able to sort out what has caused what?
Will we actually discover a "bounce" or a "bump?"
Probably not. Polling over Labor Day Weekend is always a problem. We confront more than the usual number of people who don't respond or can't respond. People are away from their homes, heading back from summer vacation, or preparing their children for the start of the school year. In addition, the focus will shift so quickly from the Democrats to the Republicans that whatever opinions might be expressed over Labor Day Weekend might not last too long.
We've not seen this compressed a schedule ever before. In 2004, the Democrats met at the end of July, while the Republicans waited five weeks to start theirs on August 30. So we were able to measure - separately - the impact of John Kerry's choice of John Edwards for Vice President, just before the Democratic Convention, as well as the impact of the Democratic Convention itself on public opinion about them. (As it happened, neither the V.P. choice nor the convention appeared to change public opinion very much.).
In 2000, George W. Bush named Dick Cheney as his running mate eight days before the GOP convention started on July 31. The Democrats began their convention two weeks after that, and in the intervening time, Al Gore announced that Joe Lieberman was his choice for V.P. Likewise, in 1996, there were two weeks between the Republican and Democratic conventions, and Republican Bob Dole announced his choice of Jack Kemp as a running mate a few days before their convention began.
A whole month separated the two conventions in 1992. The Democrats held theirs first. And their "bounce" was one of the all-time largest ever recorded, at 13 points: in the CBS News poll, the Democratic ticket soared from 45 percent before the convention to 58 percent afterwards.
But sorting out the cause of that rise was as complicated as it will be sorting out the cause of any Democratic "bounce" -- if there is one - this year. Bill Clinton named Al Gore as his running mate on July 10, 1992, and the Democratic Convention began on July 13. Businessman Ross Perot had been running an independent campaign (and sometimes placed first in national polls). But Perot dropped out of the race on July 16 - the day Clinton and Gore accepted their nominations, and made what some took to be an endorsement of the Clinton-Gore ticket: "The Democratic Party has revitalized itself. They've done a brilliant job, in my opinion, in coming back." (Despite that statement, Perot changed his mind in October, and jumped back into the race.)
The removal of such a strong third-party candidate certainly contributed to the Democratic gains. But it also masked our ability to measure any direct impact the Convention might have had, and made it difficult to judge what Al Gore's nomination added to the ticket.
In 1988, it was the Republicans who mixed up the V.P. nomination and the Convention's impact. Democrat Michael Dukakis put five days between his announcement of V.P. choice Lloyd Bentsen and the start of his convention; George H.W. Bush named Dan Quayle as his V.P. on the second day of the GOP convention. Whatever the cause, Bush got a 13-point convention bump, just as Clinton would four years later, but polling couldn't on its own sort out what role Quayle or the convention itself played.
This has been an unusual election year - and election year schedule. News coverage - and polling - has had to adapt. With Obama expected to name his V.P. choice sometime next week, we should be able to measure its impact before the convention starts -- as long as he makes his announcement early enough. But given the compressed time frame this year, we may never know what short-term impact - if any -McCain's V.P. choice will have. The longer he waits, the more likely his announcement will come close to the Democrats' convention, or overlap with it or follow it. So the more likely any immediate impact of his announcement will get mixed in with everything else going on.
In fact, we will have to wait until about three weeks from now, to sort everything out - after the Republicans are finished on September 4!
As for the "bounce" or the "bump," a Google search finds about seven times as many references to the phrase "convention bounce" as "convention bump," So, while we may not know what - if anything - the impact of the conventions will be, we do know what we're likely to call it! And hopefully, it won't just be "noise."
By Kathy Frankovic