As Barack Obama’s approval ratings have declined over the last few months, the slide has often been explained as a result of a drop in support among independents. For example, a Reuters analysis out this afternoon states:

Obama, experiencing his first holiday season in the White House, finds himself at odds with some in the left wing of his own Democratic Party and losing the support of independent voters who were key to his 2008 election victory.

But as John Sides explains today at The Monkey Cage, it would be very hard for independents to account for much of the decline, for one simple reason: there aren’t very many true independents.

Sides notes that more people now will say, when asked by pollsters, that they are independents than either Democrats or Republicans. (This is the basis for claims by columnists like David Brooks that independents “are the largest group in the electorate.”) But it turns out that most of those folks, when pressed, will lean one way or the other—and that voting behavior, and approval trends, among these “independent leaners” is awfully similar to that of partisans. In the areas that matter, there’s just not much difference between being a Democrat and being an independent who leans Democratic (and the same goes for Republicans).

So what does all this mean for understanding the slide in Obama’s approval ratings? Sides sums it up:

Obama’s approval has gone down mostly because of trends among partisans. Combined, Republicans and independents leaning Republican account for 50% of the drop… The two groups of Democrats account for 34%. Pure independents account for the rest.

There’s much more at his full post—and it’s something to keep in mind the next time you see a headline about those all-important independents.

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Greg Marx is a CJR staff writer. Follow him on Twitter @gregamarx.