(CNN) Mike Murphy has long been on the "A" list of the Republican consulting world , having served as a lead adviser to Mitt Romney and Jeb Bush, among many others. Since the rise of President Donald Trump, he has emerged as a leading voice within the party against Trump.

Our conversation, conducted via email and lightly edited for flow, is below.

Cillizza: Over the weekend, you condemned the "larger moral cowardice that has overtaken the party" in the era of Trump. Expand on that idea.

Murphy: It's one thing to accept the normal array of slippery political cheats and dodges in the name of tribal party loyalty with the usual tired rationalization that the "other side is always worse," but Trump's activities are so corrupt and corrosive as to elevate the problem way beyond cynical politics.

Trump's actions as President have created a clear moral test: Are you complicit or are you against? Trump has gone so far -- racial demagoguery and slurs, abuse of office, dictator appeasement, nepotism and family corruption, blazing incompetence, contempt for the rule of law, betrayal of public institutions, epic dishonesty, authoritarian thuggishness... the list never ends -- that he is damaging public institutions and debasing the Presidency of the United States.

You either have the courage to oppose that, regardless of blind party loyalty, or you don't. And the bulk of our party's elected leaders are showing moral indifference and cowardice about Trump. It's tragic and sad and makes of mockery of the legitimate criticism the GOP used to level at erring Democrats. It's a stain on the party that sadly will now last.

Cillizza: How different do GOP lawmakers -- and governors, etc. -- talk about Trump privately versus publicly? And if it's different, is that delta entirely explained by fear of losing?

Murphy: I don't talk to all of them, but there is widespread contempt. They think he is vain and stupid. But many say they are powerless to change his behavior. The thinking goes: "If I publicly criticize him he won't change one bit, but I'll lose my seat in a primary to a nut and the nut will give the seat to vile socialists on the other side, who are no better than Trump in many ways. Plus we cannot let the liberal Republican-hating media 'win.' So I keep quiet while we rack up important ideological victories -- judges, regulatory reform, taxes -- and wait for this dark storm to pass."

It's a rationalization I understand, but it gives Trump a moral pass as he ethically urinates all over the institution of the presidency and (the idea of rule of law.) My response is usually that if 100 of you stood up, he would change. They reply, "Perhaps... so call me when you get the first 25 signed up and I'll think then about joining you."

Cillizza: Is there any real Republican Party aside from Trump at this point? If so, what does it look like -- and why don't we hear more about it?

Murphy: It's pretty much a Trump cult in the GOP primary electorate, particularly outside the blue states of the Northeast. He's very strong in the sunbelt, Midwest and West. But like all cults, it'll end badly. Somehow the GOP campaign mindset has gotten aligned to this stupid idea that the general election is essentially nothing more than a big GOP primary, and that primary voters are swing voters who need to be constantly sucked-up-to, while ignoring everybody else. We'll see how that works out on Election Day outside of hardcore Republican areas.

Cillizza: Let's say Trump loses in 2020. What -- if any -- is the lasting damage the Republican Party will have sustained from his presidency and the way the party reacted to it? Does that change if he is a two-term president?

Murphy: I think the bigger question is what happens if we lose the House -- and more -- in the 2018 midterms. If it does happen, such a meltdown will shake the party badly -- no political party endures a major loss without repercussions -- and Trump, the supreme magical winner of 2016, will become an epic party-killing loser. (My guess is Trump will compound this by attacking the party for its loss, since nothing can ever be his fault.)

At that point the idea of running in 2020 under Trump will look like a march to the guillotine, particularly for the GOP Senate majority. That's when Trump will find himself on the sharp end of the same kind of cynical self-preservation thinking that he's benefited from to date. Nobody in the family stands up to Tony Soprano until they stop making money and start going to prison. Then it's time for change. Tony is the last to know.

Still, if we hang on to the House by two votes, it'll read in the expectations bazaar as a big Trump comeback win and he'll probably be the nominee. Then we'll be near-certain to lose big 2020. It'll be our McGovern '72 and out of that rubble the 2023-4 GOP primary race will redefine the party, hopefully back to opportunity conservatism.

(One crazy prediction: if Trump does hang on, I predict he'll start talking about dumping Mike Pence as VP. Such a story would create irresistible drama for the reality show producer POTUS. Next year, after the media gives over-implied but loud credit to female voters for any Democratic gains in 2020, White House press leaks will start to appear indicating that while Trump likes good old Pence, he wants to shake things up and after a flurry of hysterical who's next drama in the media with various names bouncing around, Trump will eventually float the name of Nikki Haley. The media will buy it hook, line and sinker: "A clever Trump master-stroke to get back female and minority voters, blah, blah, blah." That move will also allow Trump to plunge a satisfying Shakespearean dagger of revenge into Pence, whose own future presidential maneuverings are a bit too transparent for the insecure Trump. Team Pence really needs to read a few Stalin biographies.)

Cillizza: Finish this sentence: "The Republican Party needs to be _____________ in order to survive." Now, explain.

Murphy: "The Republican Party needs to be freed of Donald Trump and Trumpism in order to survive."

It's no small thing that Donald Trump lost the popular vote by millions. He stumbled to a lucky lock-pick win in the Electoral College, but the popular vote -- and all the current polling -- shows he decided to pick a fight to the death with the fast-growing segments of the electorate. Only true suckers fight demography.

His election was a dead-cat bounce and is extremely unlikely to be repeated. I'm not sure he'll survive his first term, but if he does and can win re-nomination, he'll find a re-elect very daunting. The demography is worse and getting even more difficult every day, the novelty is gone, incompetence is always punished in the fullness of time and the staff machine that exists to prop up an existing POTUS is a weak shambles of dregs and enablers.

Ideologically, Trump has cashiered the Republican Party's longstanding equity as a force for free trade, fiscal conservatism, tough foreign policy and hard-headed competence. Trump now provides political fuel and success only to those who would destroy the conservative movement. He's driven the GOP into a moral and political ditch, which will likely in time put the county on the left's road to serfdom at least through the next political cycle. The GOP went on a wild, stupid bender with Trump and now the hangover will be very painful.