What was the principal purpose of the Republican Party?
prevent the spread of slavery
If the Supreme Court Justice does not agree with the majority opinion, than the court can write a concurring opinion.
Rewriting the entire in is probably not going to happen. It is tradition in the United States to update constitutions with amendments instead of rewriting the entire one as many people do in Europe for example. How it might be updated is unknown because the people in the future will be different than us and have different values and they'll amend it according to that.
