As Americans examine the astounding dysfunction of their government, gerrymandering is usually cited as the prime culprit. This narrative offers a compelling villain: venal politicians who draw district boundaries for partisan advantage or to protect their own incumbency.

On the surface, it makes sense that manipulating district lines could be responsible for the increase in non-competitive, non-diverse congressional seats and the rise of ideologues who take radical positions without fear of voter retribution. But this ignores evidence that gerrymandering is only partly responsible for the current partisanship — and that eliminating it will not address the calamity we are witnessing.

No one disputes that congressional districts have become less competitive. During the last government shutdown in 1995, 79 of the 236 House Republicans represented districts that supported President Bill Clinton in his 1992 election. Today, only 17 of the 232 House Republicans represent districts that backed President Barack Obama — demonstrating more partisan consistency at the district level.

Cook’s Political Report, a leading congressional handicapper, makes the point more directly. There were 164 competitive districts in 1998, according to Cook’s Partisan Voter Index, but only 99 after 2012.

While this could be due to gerrymandering, a deeper look at the data reveals a different reality. County lines do not change every decade the way congressional districts do. In 1992, Clinton won 1,519 counties while in 2012 Obama won only 693 — less than one-third of all counties. His support was far more geographically concentrated than Clinton’s.