With the GOP primary now all but officially over—congratulations, Mr. Romney—we can safely declare it swing voter season. As the general election campaign heats up, ever more attention is going to shift to that special class of voters who we presume will be responsible for picking our next President. But there’s good reason to believe that the vast majority of Americans, including professional journalists and campaign operatives, wouldn’t recognize a typical swing voter if they met one.

Indeed, the application of the term “swing voter” deserves a lot more scrutiny than it generally earns. As it is, the term is thrown around carelessly to apply to large demographically or ideologically defined groups. The most common assumption, for example, is that swing voters are synonymous with political independents, but as I explained at length in a recent book review, that is an utterly fanciful notion.

Instead, the simplest and clearest way to think about it is on the level of the individual voter. For an individual voter to qualify as a swing voter, the relevant criterion that needs to be fulfilled is persuadability. And that’s not a quality that’s exclusive only to those who are completely undecided, or who are only weakly committed to a candidate. Even those who are moderately committed can be persuaded to deepen their commitment. And the deepening of an existing affiliation with a candidate can be just as significant, both statistically and electorally speaking, as attracting mild commitment from someone who had previously been mildly committed to another candidate.

The important factor is not where voters’ inclinations started out, but the fact that their inclinations were changed at all. The act of persuading a swing voter has traditionally been thought of as moving a given voter from more likely to vote against a given candidate to more likely to vote for him—say from 55 percent likely to vote against to 55 percent likely to vote for. But it could also mean moving that voter from somewhat likely to vote for a candidate to very likely to support that candidate (say from 55 percent likelihood to 65 percent)—or, for that matter, from very likely to almost certain (65 percent to 75 percent). All three of these examples are mathematically equivalent—and it makes sense to think of them all as swing voters.  

A bit more math may help clarify the point. If there are 100 voters with a probability of just 45 percent of voting for your candidate, then you would expect your candidate to lose by 10 votes, assuming everyone voted (45 for vs. 55 against). If you persuaded these 100 voters to have slightly positive feelings towards your candidate—say, a 55 percent probability of voting for him—than he should receive a net gain of 10 votes (55 for vs. 45 against). Overall, then, as your candidate moves from 45 to 55 percent favorability, his campaign experiences a marginal shift of 20 votes—from losing by 10 votes to winning by 10 votes. Now let’s say your 100 voters start out with a 65 percent likelihood voting for your candidate—that’s a margin of +30 if they all vote (65 for vs. 35 against). If you bump up that probability to 75 percent, you now have a margin of +50 (75 for vs. 25 against). The net gain in margin from shifting probability of support from 65 to 75 percent? Twenty votes, just as in the previous example. 

Persuadability, then, is not logically restricted to voters in the center; it can potentially be far more broadly distributed. That is what William Mayer found in his analysis of swing voters based on National Election Study data. Swing voters are least likely to be found among strong partisans (12 percent of this group); more likely to be found among independent leaners (27 percent) and weak partisans (28 percent); and most likely to be found among pure independents (40 percent). But since pure independents are such a small group, they wind up being just 13 percent of all swing voters, actually less than the number of strong partisans among swingers (18 percent). Another 28 percent of swing voters are independent leaners, and the largest group, 42 percent, are weak partisans. Thus the overwhelming majority (70 percent) of swing voters are weak or independent leaning partisans—the kind of voters whose probability of support for “their” candidate is more usefully thought of as being movable from 70 to 80 percent than from 45 to 55 percent.

If swing voters are not clustered in the center of the political distribution, are they at least clustered in particular demographic groups where campaigns can get at them? Here the research also suggests that the intuitive and popular conception is wrong. According to Mayer and others, demographic differences between swing and nonswing voters are generally modest. The idea that swingers are heavily concentrated in special groups like “soccer moms” or broader ones like the white working class or Hispanics is incorrect. In reality, swing voters are scattered throughout the social structure.

Of course, even if swing voters are hard to pin down, that doesn’t mean campaigns shouldn’t try to reach them. They are by definition the most persuadable voters and, while estimates vary, in a typical campaign they might be around a fifth of voters. But given the fact that the overwhelming majority of swing voters are partisans, the logical place for a campaign to start is by consolidating support among “their” swing voters—that is, by driving up their support rates among weak partisans and independent leaners. As a bonus it would be useful if the campaign message reached toward the center and appealed to pure independents though numerically this is less important. The least promising group is clearly the partisan swingers of the other side. Whatever message might chip away at this group’s support for the opposing candidate seems unlikely to be the same message that would consolidate weak and independent leaning partisans behind a campaign’s candidate.

The same “one size does not fit all” applies to the demographics of swing voters. Since swing voters are everywhere, a campaign might be concerned with reaching swing voters among both Hispanics and the white working class. But it seems unlikely that the same message, especially of some ill-defined centrist variety, will appeal strongly to swingers in both groups. Boringly, it may come down to the mundane task of setting support rate targets among these and other demographics and figuring out how to hit each of the targets. But however boring it may seem, that’s how you win elections.

Ruy Teixeira is a Senior Fellow at the Center for American Progress and editor of America’s New Swing Region: Changing Politics and Demographics in the Mountain West, to be released by Brookings Press in March.