Donald Trump speaks at a campaign rally in New Orleans. (Gerald Herbert/Associated Press)

Danielle Allen is a political theorist at Harvard University and a contributing columnist for The Post.

To all those who oppose Donald Trump: Stay the course.

From Thursday to Sunday, Trump performed his most impressive run of pirouettes to date. On Thursday, at the Republican debate in Detroit, war crimes were in, as they have been since November. On Friday, in a statement to the Wall Street Journal, they were out. On Sunday, in a “Face the Nation” interview, they were back in, except they wouldn’t be war crimes anymore because Trump intends to change the law to make, “at a minimum,” waterboarding legal.

Since November, Trump has repeatedly argued for bringing waterboarding and “more than that” back. Since December, Trump has repeatedly declared that the fight against terrorism requires killing the families, including children, of terrorists.

Both actions are against international and domestic law, and soldiers can be found guilty of war crimes if they obey an unlawful order.

Donald Trump drew swift condemnation after images of supporters raising their right arms and swearing to vote for him emerged on March 5. (Peter Stevenson/The Washington Post)

Since December, people have been telling Trump that he has proposed war crimes, and last month, former CIA director Michael Hayden said the military would not carry out such orders.

At Thursday’s debate, when Trump was asked whether he still maintains his commitment to targeting the families of terrorists, he insisted that he did. He was asked what he would do if the military refused to carry out similarly illegal orders to torture. He said: “I’ve always been a leader. I’ve never had any problem leading people. If I say, ‘Do it,’ they’re going to do it. That’s what leadership is all about.”

Then, in a statement to the Wall Street Journal on Friday, he retracted, or seemed to do so, saying, “I will not order a military officer to disobey the law. It is clear that as president I will be bound by laws just like all Americans and I will meet those responsibilities.”

On the same Friday, at a rally in Michigan, however, he said: “Waterboarding is absolutely fine, but we should go much further.”

And on CBS’s “Face the Nation” on Sunday, he said this: “Now, I will always abide by the law, but I would like to have the law expanded. . . . Right now, basically, waterboarding is essentially not allowed, as I understand it. . . . I would certainly like it to be, at a minimum, at a minimum to allow that.”

If you had happened to read the Wall Street Journal report but missed the televised debate or Sunday interview, you might have been inclined to breathe a sigh of relief. “Oh, thank goodness. Torture is out. War crimes are out,” you might have thought.

But you would have been wrong to let down your guard.

Trump speaks out of both sides of his mouth so frequently that it is unreasonable to credit what may at first appear to be morning-after disavowals.

His first thoughts reveal his instincts. His second thoughts may go a different direction, but, don’t worry, there will be third and fourth thoughts, and they point right back to the first thought.

Trump’s first thoughts tell you all you need to know.

His instincts are to violate freedom of association and freedom of religion, as he revealed when he refused to rule out the registration of Muslim Americans.

His instincts are to violate freedom of the press, as he revealed when he called to open up libel laws to restrict the capacity of the media to say negative things about him.

His instinct is to call for the killing of innocents.

He praises the leaders of China who massacred their own citizens in Tiananmen Square.

He said that a protester “should have been roughed up” and that it was better in the “old days” when protesters would have been “carried out on a stretcher.” This is to condone unlawful violence, something that the leader of a democratic republic should simply never do. Not even once. Not even on the campaign trail. It’s far worse than the comments about his body parts and is, in my view, disqualifying.

All these unacceptable remarks are just versions of Trump’s fundamental failure to respect the law as the guardian of people’s rights.

We all know how he has doubled down on and then folded on many of these positions. He disavowed the registration of Muslims. He made sure to wink at David Duke before finally fully disavowing him. To avoid having to release the transcript of his off-the-record conversation with the New York Times, he now claims to respect the media. At his rallies, announcers now instruct audience members “not to touch or harm the protester” but to draw the attention of security officers.

He has, however, not yet disavowed his praise of the perpetrators of the Tiananmen Square massacre nor his decision to distribute a Mussolini quotation. And although it seemed that he was going to disavow torture, he instead proposes to legalize it. Would anyone be surprised if he did the same with the proposal to target terrorists’ families?

These acrobatic leaps should not be interpreted as meaning that Trump has learned something, that civics lessons in legal structure, constitutionalism and war crimes are sinking in. People have been schooling him in these lessons since December. He has to have known all along that what he has been proposing is unlawful.

Nor should the turn-and-turn-about routine be interpreted as an example of worthy flexibility, of coming to believe that a new position is better than the first one.

Instead, we should interpret the acrobatics as shifts in Trump’s negotiating position. Instead of negotiating with the lower-income, high-school-educated whites who have made up his base so far, he is preparing to negotiate with the rest of us, the ones who have been pressing the constitutional issues. He’s giving us back lawfulness, or so he means to make it seem, like a hostage-taker whose kindness we should now appreciate.

And this leads us to see the core of his instinct. In his self-praise of his deal-making abilities, he makes it clear that he believes that you should start any negotiation from an extreme position and move from there.

What is the extreme position with which he began this campaign? Trump has told his base that he is willing to put the very Constitution on the table on their behalf. This has quite reasonably provoked considerable fear and anxiety among the rest of us. On Friday, he appeared to take the Constitution and lawfulness off the table and, presumably, we were all supposed to feel relieved.

But a negotiator’s first position is credible only if he is willing to act on it. This means we have to understand Trump as willing, in principle, to act on the threats he has made to lawfulness and to the Constitution — as he has just declared he is for waterboarding. This already turns our Constitution into something dependent on his arbitrary will. If it’s still safe, we are given to understand, it’s only because he hasn’t yet decided to act on his threats to it.

One reason constitutional government is such an extremely valuable possession is because it lessens the uncertainty of the social world. The point of having a constitution is to get rid of arbitrary power.

In the American Revolution, the colonists sought to overthrow a king who had, as Thomas Paine put it, “a thirst for arbitrary power.” Trump deserves to be on history’s list of individuals with such a thirst.

The way this Trump campaign feels is what arbitrary power feels like. This is what a Trump presidency would feel like, too.

To all those who oppose Trump: Stay the course. Don’t let his acrobatics fool you. We should all recognize the techniques of a habitual abuser when we see them.