[Dalek]

The judicially-activist (i.e. in clear defiance of the language and legislative intent of the 14th Amendment) Slaughterhouse cases laid the groundwork, in that they were inevitably overturned, thus creating an opening for constitutional interpretation that erred as far in the other direction.

[PapaNew]

Unfortunately, the 14A was famously badly and hastily written. However, despite what law schools might teach, Slaughterhouse (1873) was certainly not judicial activism but had sound constitutional reasoning as to the best findings of the intent of the ratifiers of the 14A passed five years earlier. Of course, as with almost all SCOTUS activity in the 20th Century, the overturning decades later of Slaughterhouse precedent had no constitutional-based explanation.