Closed primaries - not gerrymandering - leads to a polarized Congress

That's the argument made in this National Journal article - building off a post below. Closed primaries allow ideologicaly polarized party identifiers to dominate gets to run in the general election. They shut out the moderate voters - a point we make at various points in class:

Congress is now akin to a parliamentary legislative system, where nearly all Republicans are conservative and most Democrats are liberal. For most of American history, that wasn’t the case. Parties, historically, were ideologically diverse coalitions cobbled together by powerful leaders. Before legislation came up for a vote in Congress, it had to pass muster with the majority party’s members, making ideologically polarizing legislation tough to implement. Rockefeller Republicans and conservative Southern Democrats were a pivotal part of their parties up until at least the 1980s, and served as moderating mechanisms to partisan overreach. Over the last two decades, however, many of the last conservative Democratic holdouts in the South retired, lost to GOP opponents or switched their party affiliation to Republican. Liberal Republicans are now all but extinct. The fights in Congress aren’t about regional self-interest; they’re all about ideology.

At the same time parties are becoming increasingly ideologically homogeneous, more and more Americans are identifying themselves as independents. An August 2012 Third Way study found that both Republican and Democratic registrations dropped from 2008 to 2012 in five of the eight battleground states that register voters by party, while independent registrations jumped in six of the eight. In the states wher parties hold closed primaries, the voter pool is more ideologically driven, making it more likely a hard-core liberal or conservative will emerge from the primary, no matter how competitive the district is. That’s true in 24 states for Republicans; 19 for Democrats.

Both registration trends and polls testing ideological identification show that, even in partisan, gerrymandered districts, there’s demand for more centrist candidates, if elections were designed in a way to empower more-moderate voters.