WTF Happened in 1971? (2019)
This video has a nice summary of all the changes in the 1970s, and how many other prominent authors have documented that radical  shift.
<a href="https://www.youtube.com/watch?v=1gEz__sMVaY" rel="nofollow">https://www.youtube.com/watch?v=1gEz__sMVaY</a><p>The author believes the problems can be traced to the US congress switching from closed (anonymous) to open voting on January 3rd, 1971<p>Somewhat related, this post shows how the US congress has grown incredibly divided over time
<a href="https://www.realclearscience.com/journal_club/2015/04/24/political_partisanship_in_three_stunning_charts_109196.html" rel="nofollow">https://www.realclearscience.com/journal_club/2015/04/24/pol...</a>