I SUPPOSE WE should be grateful to Linda Killian. Her new book collects in one place every clichéd and suspect empirical generalization about political independents. So in that sense—and only in that sense—it is a useful volume.

Start with the premise of the book. It is that independents are all swing voters ready to move right or left politically—or in Killian’s feverish imagination, toward some inchoate centrist formation of the No Labels variety. This premise is based on the greatest myth in American politics: that independents are actually independent. They are not. As numerous studies have shown, the overwhelming majority of Americans who say there are “independent” lean toward one party or the other. Call them IINOs, or Independents In Name Only. IINOs who say they lean toward the Republicans think and vote just like regular Republicans. IINOs who say they lean toward the Democrats think and vote just like regular Democrats.

Just how strong is this relationship? In 2008, according to the University of Michigan’s National Election Study (NES), 90 percent of independents who leaned Democratic voted for Obama, actually a higher level of support than among weak Democratic partisans (those who said they were “not very strong” Democrats), 84 percent of whom voted for Obama. Among Republican-leaning independents, a still-high 78 percent voted for McCain, compared to 88 percent support among weak Republican identifiers.

Evidently, these two groups are quite different animals. On the one hand, we have a group of “independents” who voted 90 percent for Barack Obama. Moreover, as Alan Abramowitz and others have shown, the policy views of Democratic-leaning independents look just like the policy views of Democratic identifiers. On the other, we have a group of “independents” who voted 78 percent for John McCain and have policy views that look just like Republican identifiers. Clearly it does tremendous violence to the data to lump these two disparate groups together and give them a label—“independents”—that implies they do not have partisan inclinations.

Yet the “independent” group does include one sub-group whose members look and act more like swing voters. This is the so-called pure independents subgroup, those who say they do not lean toward either party. In 2008, they split their vote much more evenly between the parties—51-41 for Obama—and they have policy views that are not closely aligned with either party. But this is a small group, and because it tends to show low information, low involvement, and relatively low turnout, it is even smaller in the context of an actual election. In 2008, according to the NES, they were just 7 percent of all voters and only 20 percent of nominally independent voters.