The GOP was dead when Reagan left office in 1989. After Reagan got 2 terms, the GOP Establishment determined, "we ain't never gonna let THAT happen again!" And they haven't.
1988 Bush I, 1992 Bush I, 1996 Dole, 2000 Bush II, 2000 Bush II, 2004 Bush II, 2008 McCain, 2012 Romney, 2016 Trump....
ALL have been Establishment GOP (some worse than other, obviously), except Trump, who was a Democrat until 2-3 years ago, and he is really a populist with a nationalist streak. NONE have been Conservatives in the mold of Ronald Reagan.
The GOP as a party has not stood for Conservative Principles since they took over Congress in 1995, for the first time in 40 years, and passed 7 of the 10 points of the "Contract With America." And after they did that, they let Bill Clinton take the credit, and bowed to him for the rest of his Presidency. They even allowed him to shut down the government and blame them.
By 1996, I resigned by position as a County Executive Committeeman in the SC GOP and left the party. The Establishment is too entrenched. They fixed the system after Reagan so that Conservatives cannot get the nomination. Trump -- he was, and is, an anomaly, that they haven't figured out yet. Truthfully, were it not for open primaries in a number of States where Independents and Democrats could crossover and vote in the GOP primaries, I doubt Trump could have won the nomination. But it is absolutely certain a Conservative NEVER will again.
The GOP Establishment want nothing more than to thwart Trump where he wishes to upset the Status Quo. No change to ObamaCare, Taxes, etc. They are as much a part of the system -- and the problem -- as Democrats are. In that much, Trump deserves the support of Conservatives -- although we may not support his specific "fixes" of those problems. We'll see.
Bottom line: The GOP will have to die and a new 2nd Party will have to emerge to take it's place before the Status Quo can ever change. And so many millions are so entrenched in the current status quo that it may take civil war to rip them away from it.... That's what happened the last time a new party entered the system: The Republicans.