Some elections are about persuasion. This one is about turnout. In past presidential debates, candidates have tried to change people's minds and win over undecideds. In this year's presidential and vice presidential debates, the candidates have tried to increase the enthusiasm of their base.
The results have shown up in the polls, most vividly in those polls that don't weight the results to match the party identification of the last couple of elections.
Thus, George W. Bush zoomed up in some polls right after the Republican National Convention. The first post-convention Gallup poll had him ahead of John Kerry by 52 percent to 45 percent, compared to a 48 percent to 46 percent lead before the convention.
Gallup is volatile because its likely voter screen is very tight, so that not much more than a majority of registered voters are classed as likely voters. The post-convention sample had more Republicans and fewer Democrats than the pre-convention poll. That's evidence that Republicans felt a lot more enthusiastic about their president after the convention than before.
Similarly, Gallup showed Kerry spiking to a 49 percent to 49 percent tie after the first debate, as compared to a 52 percent to 44 percent Bush lead in Gallup's last pre-debate poll. That's evidence that the balance of enthusiasm tilted toward the Democrats after the debate.
Pollster John Zogby, who weights his results by party identification, shows much less movement. Starting with a poll taken during the convention, Zogby has shown Bush at 46 percent and Kerry between 42 and 45 percent.
Who is right? The answer, I suspect, is somewhere in between. Zogby has got it right in one sense: very few Republicans are abandoning Bush, and not many more Democrats are abandoning Kerry.
But Gallup also has a point. Republican and Democratic turnout is not the same year after year. The 2000 VNS exit poll sample was 39 percent Democratic, 35 percent Republican. But in 2002, the turnout was apparently more heavily weighted to the Republicans, though we're not sure because the exit poll was flawed and not conducted in every state.
As for this year, no one is sure. Both sides are paying unprecedented attention to turnout. The Bush campaign from the beginning has devoted far greater resources than previous Republican campaigns on voter registration and turnout operations. Bush spokesmen say they have attracted more than 1 million volunteers, with more than 50,000 in critical states like Florida, Ohio, Pennsylvania and Michigan. Democrats are also devoting more resources to registration and turnout than in previous years. They are relying on the labor unions, which have been their mainstay in the past, and also on liberally funded 527 organizations.
There is also a difference in motivation on the two sides. Democrats are motivated more by hate -- not too strong a word -- of George W. Bush than they are by positive feelings toward John Kerry, the candidate they settled on quickly to avoid the electoral disaster they thought they'd face if they nominated Howard Dean. Republicans are motivated more -- not by love, that is too strong a word -- but by affection for George W. Bush, and for the way he has stood up under the attacks of his opponents and the media.
That affection seems likely to be strengthened by Bush's performance at the second debate in St. Louis. Bush showed a sense of command and a command of facts and argument much greater than he had eight days before in Coral Gables, Fla. He seemed at ease and even cracked jokes.
John Kerry, on the other hand, often seemed on the defensive and fell into the habit of repeating himself that hurt Bush in their earlier encounter. His stentorian tones were unleavened by humor.
As this is written, no poll results have been announced, but my guess is that the balance of enthusiasm is likely to tilt toward Bush by about the same amount it tilted against him after the first debate. If that's right, Bush's numbers are likely to spike upward in the Gallup poll and to rise slightly in polls that weight for party identification.
But that may not be the final move. The balance of enthusiasm can change quickly, as we have already seen. And any significant change could change the outcome of this election.