> If the politicians of a particular era were elected their policies must have been within the window of that era.
Sure, they're probably somewhere _within_ that window, but that tells us nothing about the boundaries of the window. Which politician gets elected depends on factors like funding, news coverage, campaign strategy, how districts are divided and how votes are weighted. Especially at the national level. Which policies an elected official implements is dependant upon lobbying, cooperation with other politicians, and legislative work that's going on at a particular time.
> If all the politicians, of all parties, in an earlier era were to the left of today it stands to reason that the range of policies acceptable to the public, ie the window, has moved to the right since then.
All politicians? That's a lot of people to consider, but I suppose that we don't have anyone in the west running on a fascist platform, even though that was popular in the early 20th century. I haven't seen any absolute monarchists, plutocrats, theocrats, or ethno-nationalists either. Nowadays monarchs are symbolic rulers and "plutocrat" is just an insult.
Those positions are all to the right of where we are today, and they're now well outside of public discourse. So, politicians of the past weren't all more left-leaning.
> Young people of the right agree just about as much as those of the left. Older generations of right and left are those holding the previous anachronistic views.
Exactly! Whether you're looking at Labor voters, Democrats, Republicans, or Independents, they've all shifted their views to the left, compared to where we were a few decades ago.
I'm not saying that individual people have changed their minds on social issues. We should expect to see old people that still have the same beliefs that were common during their formative years. Society as a whole has shifted as younger people grow up with a different value system and old people die off.