Even if pollsters would prefer that you look at their polls as a snapshot of where the race stands rather than as a crystal ball showing where the race will end, it's only natural to wonder, when you see a certain poll result, how it may approximate the final result. It's on this point that critics of Gallup sharpen their claws. The critics charge that in the early part of the race -- weeks before the election, say -- Gallup's "likely voter" methodology often results in numbers that look extremely unlikely to come about on Election Day.

Ruy Teixeira, a Democratic polling expert and Web pundit, is chief among these critics. He points out that in the last three presidential elections, the pattern in which voters in exit polls identify themselves as either Republican, Democrat or independent hasn't changed much. In 1992, 34 percent of the voters called themselves Democrats, 34 percent said they were Republicans, and 33 percent claimed to be independents. In 1996, 39 percent were Democrats, 34 percent were Republicans, and 27 percent were independents. In 2000, it was roughly the same, with 39 percent Democrats, 35 percent Republicans, and 26 percent independents. Teixeira says that these numbers show that, over time, how people think of themselves politically remains fundamentally steady. If you're a Democrat, you're a Democrat, and you'll call yourself a Democrat for a long time -- even if, say, 9/11 persuaded you to vote for a few Republicans, you'll still think of yourself as a Democrat. What this means, Teixeira says, is that in a sense we already know something about what we should expect to see on Election Day -- in all likelihood, we'll have slightly more Democrats at the polls than Republicans, and more Republicans than independents.

But Gallup's likely-voter results of Sept. 17 show far more Republicans than Democrats. Forty percent of the people whom Gallup tagged as likely to vote identified themselves as Republicans, 33 percent said they were Democrats, and 28 percent called themselves independents. As Teixeira sees it, this result could mean one of two things. The first is that a fundamental shift has occurred in the electorate, a recent event that turned a lot of Democrats into Republicans. Teixeira calls this idea ludicrous. "Does it make sense to have a change in party I.D. over this short period of time?" he asks. "I don't think so. I don't think it switches this much that fast."

The other possibility, the one that Teixeira says is more probable, is that Gallup's likely-voter method is biased. In short, he believes that the battery of questions Gallup asked its respondents in mid-September to determine whether they were likely to vote was allowing more Republicans into the likely-voter pool than Democrats. "They ask the questions in such way that what you get in the likely pool is one form of political interest," he says. "And it doesn't take much, because of the low response rates. Any kind of partisan behavior is going to produce a partisan result. All of that bias gets imported into your poll."

Teixeira doesn't think that Gallup's likely-voter methodology is biased in favor of Republicans per se. Instead, he says, it's biased in favor of the "more activated" party, the one that that feels more enthusiastic about its candidate. His idea is that voters who feel good about their candidate probably have an easier time answering the questions Gallup uses to determine who's going to vote. If you were excited about Bush's performance at the Republican Convention, you may have gone and found out where your polling place is and you may tell the interviewer that there's no way you're going to miss voting on Election Day. Meanwhile, if you're a Kerry supporter and Bush's convention speech demoralized you, gave you the idea that your candidate could never beat him, you may have become apathetic about the project of voting. You don't care where your polling place is; you're not even really thinking about the election. In this example, the Bush voter would be counted as likely; the Kerry voter unlikely. And even though no voters have really changed their preferences -- the Kerry voters are still sticking with Kerry, the Bush voters sticking with Bush -- Bush will suddenly appear to be doing better in the polls, because his voters are now considered likelier to vote.

This is no idle theory of Teixeira's. In a forthcoming paper in Public Opinion Quarterly, the bible of polling research, the political scientists Robert Erikson, Costas Panagopoulous and Christopher Wlezien report on a study they conducted of Gallup's likely-voter model during the 2000 presidential election. The likely-voter poll that year, they note, resulted in extraordinarily volatile shifts in opinion. On Oct. 3, 2000, the day of the first debate, Bush trailed Gore by 51 to 40 among likely voters. But a few days later, Bush was ahead, 49 to 41. Did people really swing so suddenly from Gore to Bush? After analyzing data provided by Gallup, the scientists conclude that such a shift did not occur. "Our evidence suggests that shifts in voter classification as likely or unlikely account for more observed change in the preferences of likely voters than do actual changes in voters' candidate preferences," they say. Much of the volatility in the poll "is an artifact of classification" and not the result of people changing their support from one candidate to another.

Gallup, for its part, doesn't dispute this idea. To Gallup, stronger results should be reported for a candidate whose base is "more activated." A candidate who has more "likely" voters would indeed probably win the election if one were held today. In the two polls that Gallup has conducted since the Sept. 17 poll, Kerry's base has been the more activated and, consequently, better represented in the likely-voter pool. In the poll released on Sunday, Kerry is tied with Bush among likely voters; but among registered voters, Bush is ahead by a couple of points. This means that Gallup deems at least some of Bush's voters "unlikely" -- and, considering that Bush's debate performance may have demoralized some of his voters, that's a reasonable assumption, isn't it?

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