The word in Washington is that Donald Trump will deliver a unifying inaugural speech after he accedes — at precisely noon — to the presidency. And that he will pivot to a proper presidential persona.

Certainly the oath Trump is about to take — the affirmation required before he “enter on the execution of his office” — ought to be the occasion of national unity. It’s an oath to preserve, protect and defend the Constitution.

What makes it so unifying is that every officer of the United States — every legislator and judge, not just of the federal government, but of the state and county governments — must be bound by oath to support the Constitution. New citizens, too.

So why are the Democrats so bitter? Why are some 50 members of Congress vowing to boycott the inauguration? Why is California hiring a former attorney general to fight the new administration? Why the incessant weeping and wailing?

The most persuasive theory is that it has nothing to do with meddling by the Russians or James Comey or the crustiness of Trump’s campaign or his personal behavior. Rather, it’s something other than politics. It’s almost psychiatric.

This was an insight I first heard from one of my journalistic mentors, Robert Bartley, editor of the Wall Street Journal. Shortly before he died, he wrote two columns on the anger of the Democrats.

Bartley comprehended that the Democrats’ fury went beyond politics and “must have deeper, subconscious roots.” His theory was that they were unable to deal with a sense they were losing their “birthright.”

What he meant was that, as he put it, “base Democrats think of themselves as the best people: the most intelligent and informed, the most public spirited, the most morally pure.” If that’s what’s at stake, no wonder they’re so devastated.

At the time Bartley wrote those columns — late 2003 — the Democrats were gearing up to run John Kerry for president. They seemed as confident of impending victory then as Hillary Clinton was just three months ago.

But, as Bartley warned in a particularly prophetic column, that confidence belied the weakness of the glue that held together the party’s coalition. The Democratic Party, he wrote, “has descended into a collection of interest groups not bound together by any ideals.” It was floundering before the American people.

“We see scions of inherited wealth berating the ‘rich,’ ” Bartley wrote. “We see supposed champions of civil rights standing in the schoolhouse door to prevent vouchers that might give a break to black children in the District of Columbia.”

How those words echo today, as, say, a visionary advocate of school choice (and a billionaire to boot), Betsy DeVos, is up for confirmation as secretary of education. And as the rest of Donald Trump’s cabinet of millionaires enrages the Democrats.

Bartley was particularly withering on the betrayal of JFK’s vow — made in his 1961 inaugural address — to bear any burden in the cause of liberty, which the Democrats were, when Bartley wrote, then abandoning in Iraq as they had earlier abandoned in Vietnam.

“Yes, above all the war,” Bartley wrote. “The self-identity of the Democratic base is still wrapped up in Vietnam,” which had started as a “liberal, Democratic war” and could only be abandoned by “assertions of a higher morality.”

And now Trump is working with Congress on Kennedy-Reagan-style tax cuts. It’s just too much for the Democrats. They can’t process it. They may actually believe that the election is illegitimate.

All the greater the logic of a unifying speech — and policies. If Trump gets the tax cuts and deregulation he wants, America will get the investment and jobs growth we need. America will be eager for immigrants.

To those who’ve been cast from power, I can hear Bartley’s advice as clearly as I heard it when the shoe was on the other foot and the party I was rooting for had lost: Don’t be afraid of the wilderness.

Bartley was loved for the strength and optimism he maintained during his wilderness years. He knew its miseries but also its joys, including the chance to think, to experiment and to regroup.

The Democrats won’t be the only ones in the wilderness, either. Plenty of Republicans were routed by Trump. My own guess is that he’ll come to need them both. It’s a time to remember that they’ll all have been sworn to the same parchment.