Anyone who believes two major political parties could literally switch ideologies is an absolute moron and not worth typing out a post that explains as much.
If I were to ask you which party were more sexually permissive, what would you answer? Has that always been so?
I heard a story about a month ago, which provides an example. The Republicans held the Massachusetts legislature for decades after the Civil War. The Democrats, led by Tip O'Neill, finally captured it in the 1948 election, running in part on a platform of accusing the Republicans of being in favor of legalizing birth control devices.
You see, in 1948, the Republicans were mostly in favor of legal birth control, while the Democrats, then the more devoutly religious (i.e., Catholic) of the two, were strongly opposed. Seven decades later, it feels like the Republican stance has barely moved, at least at the national level, while the Democrats have gone from being more prohibitionist than the Republicans to being more libertine. This is of course a fairly petty example. But it is one example.
A senator once said of spending, "A million here, a million there, and pretty soon you're talking about real money." By analogy, an issue here, an issue there, accumulating over time, and pretty soon party ideologies are barely recognizable from what they were a lifespan ago.