I'll admit I've written about this before, but my point isn't to say it's not a big deal, but to note relevant facts when identifying the problem and the solution.
https://community.cbr.com/showthread...er#post3720119
There are several misunderstandings here.
Geographic sorting is an explanation for why someone can win the popular vote and not win the majority of the legislature.
I've used reliable sources to show how it works. When I argue that gerrymandering only gave Republicans a few net congressional seats, I back that up. A wrinkle is that Democrats also gerrymander, but for various reasons, they can't be as effective at it.
Fivethirtyeight had a program demonstrating that there would be limited gains (2-4 congressional seats out of 435 total) for Democrats if districts had been made without regard for which political party benefits, to be compact (using an algorithm) or to be compact while following county borders.
https://projects.fivethirtyeight.com...tricting-maps/
So this does mean that in order to have a system where the party that wins the popular vote has a larger share of the House and Senate, you have to specifically engineer that outcome. We should be open about that.
The increasing competitiveness of suburban areas would be something Republicans would have been unable to prepare for when redistricting after the 2010 census. That would help Democrats in legislative races in suburban districts.
But the consensus among political scientists is that geographic sorting hurts Democrats disproportionately. Anything that isn't random is vulnerable to disparate impacts. African-American voters are more likely to support Democrats than white voters are to support Republicans. Democrats are sometimes going to move to liberal enclaves, like a college town within a conservative district. Anything nonrandom is likely to affect some groups more than others.
https://fivethirtyeight.com/features...ity-districts/
https://www.propublica.org/article/t...ocrats-bad-map
It's perfectly fine that we need to argue that we change the status quo to reduce the efficiency gap. There are going to be some consequences if communities of interest are split to create more competitive districts.
Democrats gerrymandered as well. They've admit it in court.
https://www.usatoday.com/story/opini...umn/467349002/