I can't comment on the sensitives of discussing politics in America being an Aussie. I was always taught it's taboo to talk about religion or politics, so i try and stay away from it in all its forms in life (written and oral).

Having said that, i think it would be sensible to remove any bias which may come from being 'associated' with the Republicans. Can't you just say i started a book club focused on political education and that raised money for spouses of servicemen? You don't have to say it was a republican book club (unless it was actually called that - "the republicans book club"). Just call it by whatever name the book club has - genercise it.

Of course the other way to deal with this is to apply for schools that are located in strong Republican states

Most adcoms try their best at putting together diverse classes each year.....which means taking people from many difficult backgrounds. And one of the most under-represented groups can often be political professionals. They tend to stand out often in the crowd of finance/consulting/IT...

I would consider making in a focal of your application...and it seems like it may be a great essay topic as well.

Good Luck!