The 1980s were one of the least polarizing decades since the 50s at least when it comes to the public.
I very much agree with this. The 1980s were the Second Era Of Good Feeling.
Somewhere, politicians of both parties (although it was, arguably, the Republicans first) came to the conclusion that bipartisanship led to "win-win" situations where your rival won along with you. That meant it would be harder for YOU to become Governor or President when you were a mere legislator. Working together to help the President or Governor achieve something positive doesn't help a Senator, Representative, or State Legislator move up, unless their goal is to move up the legislative leadership ladder, and even then, there are backbenchers with delusions of grandeur that view bipartisanship as an obstacle to their ambitions.
