and polarization. Clinton actually ran on running in the center.
I suspect that it is the parties, not the administrations that have changed. If you look back at the Congress in the 1970s or even 1980s you would see that there were both liberal Republicans (Jacob Javits) and Conservative Democrats ( many of whom later changed party). Now, on almost any scale based on votes, you have all the Congressional Democrats on one end and all the Congressional Republicans on the other -- with a pretty big gap in between.
This means that the entire agenda changes when the President, the Speaker and/or the Senate Majority Leader changes. It is no longer the preferred solution, but the very goals that change. Consider that in 2009, we started to make progress on most issues, with the republicans obstructing to try to prevent those changes. Now, they are moving things backward (from our perspective) trying to destroy any of the hard fought progress. As long as the two parties are so polarized, this will continue. The only thing that keeps each side from legislating what its "extreme" (for lack of a better word) wants is that they will need almost all or all of their legislators (and maybe a few in the Senate from the other side) to pass most pieces of legislation. Given the polarization, the cloture rule (which is endangered) is more important than ever.
Two other massive changes are that the amount of money in politics, always too high, is now absolutely massive and that progressively since the late 1980s, we more and more Republicans watching their own media - where Fox and RW media have formed an echo chamber where each validates each other. Under Trump, this took another step where it is not the Rush Limbaugh clones saying that what we used to just call the media is lying, but the President of the United States. (I turned the car radio to one such channel briefly and heard a man indignantly complaining that saying 17 intelligence agencies was a Clinton lie -- and that the left continues to lie "even after the PRESIDENT OF THE UNITED STATES disputed that." He went on to act shocked that anyone would question the truthfulness and accuracy of the august POTUS! Something tells me, they did not speak like that in 2016!)
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