A fair and accurate assessment of party development.
My core point is direct and simple. Post-Civil War Industrial Capitalism evolved from the pre-Civil War Merchant Class. It was aided and abetted by a progressive mentality which the Republicans provided through their executive action, legislation and judicial rulings which centralized power in DC and eviscerated the vision of our Founders.
But the Republicans were not the sole party of “leftism” of the latter half of the 19th century, however that could be defined at the time. The Democrats had their populist uprisings as well. It is a complicated subject.
Unfortunately, not ridding the nation of the yoke of slavery at our founding (as warned by John Adams, who could be described as “Conservative”) set us up for the disaster of the future Civil War. With the States’ Rights folks deciding to make that their live or die cause, it would be hard to disagree now that it was an institution that had to be brought to an end. Of course, the price of doing that was planting the seed for an ever-growing tyranny at the federal level.
However, if things remained as they were pre-Civil War, where each state was viewed as one’s own country, it may have become harder and harder to deal with the challenges for a united front in the 20th century. The key, of course, is trying to find a happy medium where there is balance between the levels of governance while being able to rise to those aforementioned challenges.
Not rolling back overreaches at the federal level over the past century has been the single worst development, and both parties bear the responsibility for allowing this to happen.