Debates are followed by “instant reaction” polls of debate viewers, taken overnight and posted the day after. These have some value in capturing opinion of those so interested they actually watched the debate. But this is a poor measure of the impact of the debate, which to be meaningful neeeds to be lasting. Debate performance is as much, or more, about launching the next month for the campaign as it is about the snappy line of the moment.

Thus there is more than the usual need for a slow polling look at the debate. Now, nearly a month after, do we see any meaningful shift in candidate standing with voters? And was the response steady over time, or a blip that quickly faded? On the eve of the second debate, let’s get a clear view of the impact of the first debate.

A month before vs. a month after

I look at the polls taken in the month (26 days) following the debate, Aug. 24 through Sept. 18 (the most recent poll as of Sept 21), and compare polls taken in the 28 days prior to the debate (July 25-Aug. 22). Let’s call these the “pre-” and “post-debate” polls.

First, how do the candidates stand in national polls of Republicans and independents who lean Republican registered voters? Data are from the FiveThirtyEight.com collection of national polls.

Figure 1 shows the comparison for the eight debate participants. Only Nikki Haley has a meaningful increase in support, up 2.4 percentage points following the debate. No one else changes by even a single percentage point.

The trends before and after the debate tell the same story. Haley looks to have continued to rise after the debate, while Ramaswamy has slightly declined, as has DeSantis. All these changes are small, except for Haley.

The means and medians and number of polls are shown in the table below. In contrast to Haley’s increase, Christie and Trump rise by less than a tenth of a percentage point while the rest decline, all by less than a percentage point. Pence, Scott and DeSantis have the largest declines, though even DeSantis is down by only 0.6 percentage points.

And the candidate who wasn’t there didn’t get a boost or a drop: Trump’s support changed by 0.03 percentage points.

If the debate was thought to potentially scramble the standings, it did so only for Haley, though her support remains in single digits. Pence and Ramaswamy took much of the debate time, and a good bit of post-debate commentary. Neither has seen a lasting payoff.

Quick polls get attention, but slow polls are more illuminating.