Donald J. Trump’s presidential candidacy has turned everything on its ear.

The Republican Party is at war with itself. How does the party back a presidential nominee who opposes traditional GOP orthodoxy? And just how does the party define “unity” if it cannot back its nominee fully?

Let’s play this out a little more.

What, then, about the rest of us who at the same time oppose traditional GOP dogma while also being repulsed by the very idea of Donald Trump ever settling behind a big desk in the Oval Office?

I’m trying to grasp the apparent conflict I’m enduring now as I watch Trump get ready to become the Republicans’ next presidential nominee.

I dislike the traditional GOP view on abortion, on tax policy, on wage and marriage equality, on gun control and on immigration.

I also dislike Trump’s views on at least one of those issues: immigration. The rest of Trump’s views are, to say the least, malleable. I don’t know precisely what he thinks about any of the rest of them.

Which brings me to this point. Why do I oppose this guy’s candidacy so vehemently?

I guess it’s his unfitness for the office he’s seeking.

Trump has no record of public service;  we have nothing on which to base his past performance. He has no grasp of the basics of government, let alone any idea on how to manipulate its complexities. Trump has lied constantly throughout this campaign — and until recently has been allowed by the media to get away with it.

He is a reality TV celebrity. He “owns” beauty pageants. He’s built glitzy hotels and has lived an opulent lifestyle. And American voters are supposed to relate to this?

And I haven’t yet gotten into his moral fitness for the job. He seems to possess no moral bearings. He has boasted openly about his marital infidelity. The things he has said about women simply stand as some of the most revolting things I’ve ever heard from anyone … let alone from someone on the brink of become a major-party presidential nominee.

How many other major, mainstream presidential candidates can you name who’ve spoken to shock jock Howard Stern about his sexual exploits?

This is what I mean about Trump upsetting every political calculation there is.

True-blue Republicans don’t trust him. My goodness, this guy is the classic RINO — a Republican In Name Only. Yet, he continues to collect the votes of millions of GOP base voters who, I guess, are trying to send some kind of “message” to the party establishment.

If he’s a RINO, which he is, then he ought to appeal to the rest of us who don’t swallow the Republican orthodoxy. Am I right?

Not even …