[rajin444]

> the Republicans were staunchly isolationist

They were except for their nominee running against FDR in 1940. His interventionist stance (and otherwise complete lack of political experience) made FDRs victory all but assured.

I’m not sure how you have a base so aligned on a topic that gives them an excellent chance on defeating the incumbent nominate a political nobody who holds a dissenting opinion. The same nobody who went on to serve in FDRs administration.