Democrats have often taken to complaining about how structural deficiencies in American legislative institutions cheat them out of what’s rightly theirs. In the Senate, the complaint is the filibuster (which they finally tossed aside) and lack of proportional representation. In the House, it’s gerrymandering. Liberals have been claiming for some time that the House is rigged in favor of Republicans, and that thanks to gerrymandering they can’t win a majority there. It’s false, of course, and now we have even more data to bust this particular myth.

Last year, President Obama sat down for an “interview” with his campaign donor, New Republic owner Chris Hughes. During the course of their conversation, the president complained that gerrymandering was behind the political polarization of Congress. I pointed out that, according to political scientist John Sides, who had run the numbers, this was just not true.

But the more basic complaint is less about how Republicans vote when they get to Congress and more about how they get there in the first place. Some, such as the New York Times’s Paul Krugman, still argue, against reality, that Republicans owe their House majority to “extreme gerrymandering,” in Krugman’s words. (Presumably “extreme gerrymandering” is the act of redrawing congressional districts while water skiing, or some such.) But this weekend Krugman’s Times colleague, Nate Cohn, took to the paper’s “Upshot” section to pour more cold water on the complaint.

Cohn writes:

Democrats often blame gerrymandering, but that’s not the whole story. More than ever, the kind of place where Americans live — metropolitan or rural — dictates their political views. The country is increasingly divided between liberal cities and close-in suburbs, on one hand, and conservative exurbs and rural areas, on the other. Even in red states, the counties containing the large cities — like Dallas, Atlanta, St. Louis and Birmingham — lean Democratic.

In presidential races, Democrats used to win by expanding their appeal beyond urban areas, particularly in the South, but Mr. Obama took a different path to victory in 2008 and 2012. He won the nation’s largest cities with more than 80 percent of the vote — margins that Franklin D. Roosevelt and Lyndon B. Johnson could only have dreamed of. Mitt Romney, meanwhile, didn’t win the countryside as decisively as Mr. Obama won the big cities.

The gap between staggering Democratic margins in cities and the somewhat smaller Republican margins in the rest of the country allows Democrats to win key states in presidential and Senate elections, like Florida and Michigan. But the expanded Democratic margins in metropolitan areas are all but wasted in the House, since most of these urban districts already voted for Democrats. The result is that Democrats have built national and statewide majorities by making Democratic-leaning congressional districts even more Democratic, not by winning new areas that might turn congressional districts from red to blue.

What about gerrymandering? Certainly it helps Republicans some. Can it be quantified? Cohn cites a couple political scientists who tried:

The political scientists Jowei Chen, of the University of Michigan, and Jonathan Rodden, of Stanford University, estimate that gerrymandering costs Democrats about six to eight seats in the House. Even so, “by far the most important factor contributing to the Republican advantage,” Mr. Chen says, “is the natural geographic factor of Democrats’ being overwhelmingly concentrated in these urban districts, especially in states like Michigan and Florida.”

Offsetting the gerrymandering–something both parties do–wouldn’t deliver Democrats the House. What would? Well, here is where it gets interesting. The Democrats, it turns out, are at least partly to blame for this situation. (Perhaps that explains why they cling so desperately to the gerrymandering argument.)

As Cohn explained, the Obama-era Democrats have been successful at the national level because they have pressed their geographic advantage into larger vote margins. To do that, they’ve followed a very smart playbook–but one with a downside. The Democrats nationally have pushed liberal base issues, such as social issues like the fabricated war on women and restrictions on gun rights, among others. In other words, Obama and the Democrats have moved to the left.

This was fairly obvious to anyone who wasn’t emotionally invested in the ridiculous idea of Obama as some kind of centrist or pragmatist. But it alienates voters not typically in the geographical liberal strongholds. Obama’s astute, successful campaign strategy was very good for Democrats on a national level and even at times at the state level (though the GOP has made a strong showing in gubernatorial races). But it was very bad for Democrats on a local, district-by-district level.

It was a tradeoff, and one Democrats would almost certainly believe was worth it. But now they’ve decided to complain, in a very liberal style, that there need be no tradeoffs in the real world; they want it, and if they don’t get it they must have been cheated out of it.

There’s one additional element to this as well. As Jonathan Tobin argued here last year, the Democratic complaints about the Supreme Court’s decision that Congress must revise part of the Voting Rights Act were ironic. After all that law, strictly enforced, translates into the creation and maintenance of a number of majority-minority districts. That means these minority voters, traditionally supporters of Democratic candidates, get drained from other districts to make up VRA-compliant districts. That benefits Republicans in nearby districts, but it’s Democrats who demand the law continue as it is.

So Democrats are at a disadvantage in the House. But it’s a geographic disadvantage mostly of their own making.