There is a way that the GOP can be saved. The Wall Street Journal maps it out here.
Since a Virginia court case earlier this week made it clear that a state may not enforce laws overriding the rules of a political party, it is now up to the GOP rules committee to adopt a rule allowing delegates to vote for the candidate they now believe will be the best person to take on Hillary Clinton. If the delegates vote for Trump, so be it. If not, the GOP might have a chance in November.
Right now, it is the Republican establishment and evangelical leaders who are propping up Trump’s nomination. If RNC leaders thwart the Free the Delegate movement by blocking rules changes (as they are reportedly doing right now), then they are responsible for presenting Donald Trump to the nation as the GOP standard bearer. A simple rules change will allow delegates to exercise their responsibility to choose the best candidate. Without it, Trump will become the nominee.
Evangelical leaders (e.g., Eric Metaxas, David Jeremiah, etc) who have come out for Trump have already tarnished their reputation. There is about a day left for them to recant and encourage the delegates to vote for rules changes which will allow the possibility of multiple ballots at the convention. It is simply impossible to take seriously any evangelical leaders who has come out for Trump. This election cycle has really revealed some things to the rank and file for the first time.
Check out these websites and do what you can.
Free the Delegates
Delegates Unbound
If the effort to stop Trump are unsuccessful, then consider this third party effort.