Cause and effect is not irony.
The charts people have given are examples of the reality that until the Nixon Era both the Democratic and Republican parties had right, center, and left wings. In the early 20th century, many Republicans bonded with Teddy Roosevelt to boost the “progressive” agenda, but most did not. That was a major reason why Roosevelt ran on a third party ticket in 1912. Franklin Roosevelt had several Republicans in his cabinets, because as progressives they were more liberal than many Democrats. Conservativism had multiple branches, but the most heinous were Southern racist Democrats.
Conservatism surged after WWII, partly because of anti-Communist fervor, partly because of anti-civil rights fury. Liberal Republicans, concentrated in the Northeast, lost favor to a more libertarian wing represented by westerner Barry Goldwater.
Then Nixon happened. Even for a war criminal his Southern Strategy was breathtakingly horrific. The idea was that the Republicans would accept the Democrats who detested civil rights and incorporate them into the party without any other obligation than their vote. This wasn’t a necessity. The Republicans could have just simply refused to accept them on moral grounds. Nixon had no morals, of course, so that apparently never occurred to him.
This act destroyed any vestige of a liberal wing in the party. Reagan built on this momentum to push out the moderates, who kept losing to the no-compromise right wingers. Again, the decision to concentrate the party leadership ever farther to the right was a deliberate one.
The Democrats did not do this, deliberately or otherwise. Clinton famously “triangulated,” declaring welfare over and appealing to the remaining moderates in both parties. It worked nationally, until he brought himself down. Newt Gingrich saw the strategic value of appealing to the far-right wing in his party, more numerous than the moderates, who felt themselves not being represented, until he also brought himself down. Look at that Washington Post visualizations cited by Crafter_Man and you’ll see that the split occurred during Clinton’s administration.
The Democrats had internal wars between the centrists, liberals, and progressives, but the Republicans kept moving their center farther and farther right. Trump promoted himself as the champion of the farthest right and was surprised at how successful that pose made him. He tested the edges again and again and found no resistance. Scores of acolytes realized that jumping in front of an enraged mob and proclaiming themselves as the leader won political office.
By doing so, however, they had to follow Trump’s example, which was one of shouting “NO” the loudest. This precluded any possibility of positive policies, as well as compromise, agreement, or future planning. Any and all reactions had to be visceral and immediate clickbait, inherently antithetical to rational thought, social amity, or international relations. What choice does anyone outside the bubble have except to reflexively oppose such negativity and nullification? Nothing is ever being offered that is sharable, and that too is deliberate. Any statement that would be acceptable by a Democrat is red meat to a base that refuses to accept the legitimacy of the party.
It’s nonsense to accuse recalcitrant progressives of refusing to compromise. The few progressives in office have never had power. The only resistance is exerted by rogue conservative Democrats like Manchin and Sinema. They can’t articulate their opposition as actual coherent policy, nor do they have a following or seem to represent a wing of the party. They refuse quixotically.
What’s politically interesting is that if the Republicans were to offer positive policies they might gain the advantage they seek among middle-value voters. But there seems to be nothing that would be simultaneously be acceptable to the antis that are taking over the party. Can the party survive their head swallowing their own tail? Can the Democrats ever learn to act as a party rather than multiple strands of spaghetti spilled from a package? Tune in tomorrow for the terrifying answers! Or maybe next year, or next decade.