1990s-era Democrats still had a strong presence in rural areas. But as the party moved to accommodate a more urban and liberal electoral base, its support outside of major metropolitan areas faded, especially during the Obama years.You can tell this trend is happening by what happened here in Minnesota. No one thought Tim Walz was in trouble in the 1st CD, but he nearly got beat, winning by less than 3000 votes, against an opponent who he'd beaten by 19,000 the time before. It was less than comfortable for Collin Peterson in the 7th as well; he won his district with 60% of the vote in 2012, but only 52% in 2016. And Rick Nolan barely hung on in the 8th.
Territorial representation penalizes parties for failing to build geographically broad political coalitions. So matter how lopsided a majority the Democrats can build in places like Des Moines, they will always be hamstrung if they can’t win compete less-densely populated areas as well.
I live in the 4th CD; you could put the DFL label on a potted plant and it would be elected to Congress; we've demonstrated that conclusively by sending Betty McCollum back to the Hill nine times. It's easy for the DFL to control my district, but they don't have very good arguments outstate. As we look at the new legislature in St. Paul, and the new Congress, it's the same issue. Iowa and Wisconsin were both blue states less than 10 years ago, but that's changed. It could change here, too, if the DFL learns the wrong lessons from the election.