The establishment of the republican party is a good example of

Equality or freedom are the first thing that came to my mind. It gave a different political party than democrat and allowed some people to vote more freely, and opened up many doors to quite an interesting democracy.

However mate, I think the official answer you are searching for is external mobilization, which happens when a few politicians that are not apart of teh government come together and create popular support to ultimately achieve govermental power.