Some new data from the Cook Political Report shows how overwrought this is.

In their report debuting Cook's famous Partisan Voting Index (PVI) ratings for all 435 House districts, David Wasserman and Ally Flinn also reflect upon the decline of the swing district. Twenty years ago, 164 districts had a PVI of between Republican +5 and Democratic +5 — basically what you'd consider a swing district. Today, it's less than half of that: just 72 districts.

Just look at this chart:

Gerrymandering! Right!? Not so much.

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If you look at the bottom of the chart, the biggest declines in competitive districts happened between elections — not after rounds of redistricting. In fact, 83 percent of the districts that moved out of the “swing” category — again, R+5 to D+5 — did so without being redrawn.

Only 14 districts moved from swing seats to solidly Republican — R+5 or greater — after redistricting, while 33 did so through the normal political evolution of the American voter.

Here's how the numbers break down:

Now, it's true that Republicans had a big advantage in redistricting last time around, by virtue of their huge wins in 2010. And it matters to this day. Of the 16 former swing districts that have moved to one side or another because of new maps, all but two went toward the GOP. That's going to help Republicans hold their House majority whenever if comes under attack — including possibly in 2018.

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But it's also clear that there's something larger happening here — namely, our own natural, political sorting. And that's a much bigger reason for our polarization and Republicans' House advantage than anything else.

As the South and other more rural areas such as Appalachia moved from Democrat to Republican, Democratic voters became more and more packed into smaller, urban areas. So the blue team tends to spend (for lack of a better term) more of their voters on fewer districts, because there just aren't many Republicans nearby.

Republicans, meanwhile, gained a natural — though smaller — advantage in a majority of districts across the country. I like to think of it this way: If there are 50 Democratic voters and 50 Republican voters spread across 10 cities with 10 people in each one, four of those cities would have an 8-to-2 Democratic advantage, while six would have a 7-to-3 Republican advantage.

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And even without gerrymandering, this would hold true. Gerrymandering helped solidify the GOP's majority, no doubt, but it didn't make it.

It's also somewhat faulty to argue that House Republicans are more conservative — and hence join the Freedom Caucus — because of gerrymandering. The point of gerrymandering is to draw as many safe or winnable districts for your side as you can. Often, that means spreading your voters pretty thin rather than simply making districts as red or blue as possible. And as noted, these districts would be similarly safe/conservative just because of our own natural sorting.