The game plan is destroying the front runners (Trump and Cruz) so that a "moderate" candidate can be nominated, then hoping that Hillary implodes and their candidate is elected. If this strategy fails, the GOP will go the way of the Whigs and be replaced by a new political party. Is it worth the risk?
There is no such thing as a moderate Republican anymore. Your candidates all have the same basic positions. If a Republican doesn't vote for the special interests that fund your party, than that candidate is removed in a primary. If a Republican doesn't spew the correct talking points on taxes, regulation, abortion, Islamophobia and immigration, than that candidate is removed.
The so-called establishment - think Mitch McConnell - is destroying the Constitution and leaving the Supreme Court in a crisis for over a year. This has never happened before. You are subverting the Constitution by disenfranchising the voters who elected this president to office by wide margins in two elections. Your party has become fully radicalized, from Cruz all the way to Jeb and Kasich.
The GOP will survive this election. There will always be a portion of angry, uneducated Americans who are easily manipulated by fear of the terrorist, socialist, liberal demon. There will always be a portion of Americans who give power to demagogues. The problem with Trump is that he says things out loud (-he is the oaf who doesn't know how to keep quiet in mixed company). Trump is being punished not for his positions, but because he doesn't know how to play the political language game. He doesn't have handlers to tell him how to speak about women and minorities, but make not mistake: Trump, Cruz, McConnell are the same people. At the end of the day, they are selling the same Revanchism to people with very little post high school education.
This election is not being lost by the establishment, it's being lost by Talk Radio, which has cultivated a group of voters who are incapable of selecting a viable general election candidate.