It must be stressed that at this point: we don't know. Measurements of a candidate's bounce should be based on polls taken before and after a convention. So far we have no such data--in fact, tonight will be the first night where polling can be conducted that is truly after the completeion of the GOP convention. Therefore, we won't have real bounce data for several days.

That said, let us consider the results of polls taken during the GOP convention. The one that seems to be freaking out some Democrats is the just-released Time poll. (I continue to be amazed at how easily many Democrats are panicked by the release of an unfavorable poll; there's been a lot of talk about whether John Kerry is tough enough--I'm more worried about whether regular old Democrats are tough enough. Sheesh.)

The Time poll, conducted 8/31-9/2, has Bush ahead by 11, 52-41 in a 3-way LV matchup that includes Nader. (Time presumably will eventually release the 2-way LV matchup. I'm doubtful we'll ever see RV results.) How plausible is this result?

Well, it's certainly possible that Bush was as far ahead during the convention as this poll suggests. But all other available polls taken during the convention contradict this result.

In an attempt to compare apples to apples, here are Bush-Kerry results from contemporaneous 3-way LV matchups (except Rasmussen, where only a 2-way LV result is available), with Bush's margin in parentheses:

Zogby, 8/30-9/2: 46 Bush-43 Kerry (+3)
ARG, 8/30-9/1: 47 Bush-47 Kerry (tie)
Rasmussen, 8/31-9/2: 49 Bush-45 Kerry (+4)

In this company, 52 Bush-41 Kerry (+11) certainly sticks out. Could it have anything to do with the different dates included in these surveys, even though they are very close? Well, the Rasmussen data are from exactly same period as the Time data (8/31-9/2).

But if you are skeptical of the Rasmussen data, consider the Zogby data. The Zogby data only include an additional day (8/30) when compared to the Time data. But perhaps 8/30 was a very pro-Kerry day since the Republican convention had just started. However, for Zogby and Time to matchup (have Bush leading by 11) for the three days they share, Kerry would have to be leading by about 21 points in Zogby on the day (8/30) they do not share. I rather doubt that is the case.

The simplest hypothesis then is that the Time poll, for this period, is exceptionally pro-Bush and therefore should be viewed with skepticism.

In the meantime, we will await the release of data that actually measure the convention bounce, defined, just to be clear, as the change in a candidate's level of support (not the margin) from the period before to the period after the convention. And while we're waiting, here are some interesting observations that are worth keeping in mind from a just-released Gallup analysis of the bounce issue:

Based solely on history, the Bush-Cheney ticket could expect to gain five to six points among registered voters after this week's convention. That would result in a 52% to 53% support level for Bush among registered voters, up from 47% in the pre-convention poll.

However, the results from Gallup's post-Democratic convention poll showed that history might not apply in 2004, a year in which the electorate was activated long before the conventions (usually the conventions serve to activate voters), and a year in which relatively small proportions of undecided and swing voters are available to the two presidential tickets. Also, the post-Democratic convention poll suggested that the Democratic convention might have helped energize Republican voters. It is unclear whether the Republican convention could have a similar paradoxical effect on Democrats, or if Republicans will be activated, as is typically the case.

So, stay tuned. And don't forget that even when we see the real bounce data, the pattern after the Democratic convention was for Kerry's increase in support to dissipate quickly. We shall see if the same thing happens to Bush, whatever his bounce level.

Update: The Polling Report now has the Time poll's results for the 2-way race and for RVs. For what it's worth, the Bush-Kerry RV result is 50-42 Bush, for an 8 point lead. But the anomalous nature of the Time poll's results remain.