In the 90s, the Democrats were trying to enact a single-payer health care system, and the Republican response to it was similar to what we now know as the ACA. Now, the Democrats fight for the Republican plan and the Republicans want to do away with it altogether.
Democrats in the late 60s wanted a national gun registry and ban handguns for anyone who can't demonstrate a need, with household self-protection not considered sufficient need. Any existing guns that didn't qualify would be confiscated. Republicans only wanted to ban things like assault weapons, ownership by felons, and carrying loaded weapons in public. Now, Democrats struggle to ban assault weapons, and Republicans oppose almost all forms of gun control.
FDR enacted a top marginal income tax rate of 94%. Republicans wanted taxes reduced, after the war, to a level that would pay for postwar government spending. Now, the top marginal income tax rate is 39.6%, with Democrats proposing little tweaks like increasing it a bit or increasing the payroll tax cap, and Republicans wanting to slash tax rates (I saw one the other day saying that we should aim for 1-2%) and not caring in the least about the increased deficits this would bring.
Seems to me that the American left is moving sharply right, to the point where the Democratic Party would be considered centrist or mildly right-wing by most standards, while the American right is also moving sharply right and is teetering on the precipice of going all-in on racist nationalism.