It’s tempting to hope the confirmation hearings for Judge Brett Kavanaugh will finish the way they began. That’s with what amounts to a mental breakdown by the Democratic minority.

The country deserves to get a good long look at the Democrats’ mental state as exhibited by their inchoate fury and desperation. It erupted within seconds of Chairman Charles Grassley opening the hearing. He was interrupted by Senator Kamala Harris, who wanted to delay the hearing.

Then Senator Amy Klobuchar of Minnesota, another Democrat, chimed in. When she paused, Senator Richard Blumenthal of Connecticut asked that the hearing be canceled.

All this was punctuated by noisy protesters shouting and screaming. They had to be dragged from the hearing room one by one.

The bizarre thing, as the New York Post pointed out, is that Democrats had already decided to vote against Judge Kavanaugh. They’d been inveighed to do so by no less than Senator Charles Schumer.

On one level, their desperation was understandable: A conservative majority could curtail Democrats’ ability to use an activist court to put through policies they can’t win democratically.

That’s how the Democrats won the right to abortion, say, and same-sex marriage at a time when the justices’ opinions were crosswise with lawmakers.

The party’s breakdown is the logical end point of that misguided strategy — or obsession. Democrats know that the only thing that can stop them is a constitutionally conservative court.

Yet the Democratic rage may serve only to throw into a clearer light Judge Kavanaugh’s calm, reasoned approach to the law — one focused on the plain language of the Constitution and on precedent.

This started to come into focus on the second day of the hearings.

The gravel-voiced Grassley set the tone by asking Kavanaugh about Justice Ruth Bader Ginsburg’s rule that a judge “can offer no forecasts, no hints” of how she or he will decide. A nice, bipartisan touch.

Judge Kavanaugh spoke of the importance of predictability, of litigants having confidence that justices will adhere to precedent. He stressed precedent when Senator Dianne Feinstein asked about Roe v. Wade. He noted that Roe had been upheld several times.

One such case, Planned Parenthood v. Casey, established what Kavanaugh called a “precedent on precedent.” In contrast to Justice-To-Be Ginsburg in 1993, though, Judge Kavanaugh stopped short of giving his own views on abortion.

Mrs. Feinstein also pressed Judge Kavanaugh on gun control. She had played a leadership role in the ban — since expired — on the sale of semi-automatic assault weapons.

Judge Kavanaugh had dissented when, in 2011, his court upheld new restrictions on assault weapons in the District of Columbia. He again ducked the policy question.

Instead, he focused Mrs. Feinstein on the language of the Supreme Court’s precedent in the Heller case. What a refreshing lesson in judging — and what a contrast to tantrums of the hearing’s first day.

This doesn’t mean the Democrats are done with demagoguery. Senator Patrick Leahy sought to impugn Judge Kavanaugh’s integrity by questioning his testimony for his confirmation as an appeals judge. Senator Sheldon Whitehouse implied that the Federalist Society and rich conservatives had a finger on the scale of the nomination process.

Yet my own favorite moment was Judge Kavanaugh’s answer to a question from Senator Mike Lee of Utah. That’s when the nominee explained one of the most important limits on the power of judges.

It’s that they can’t give advisory opinions, even to the president (or the Senate). George Washington himself, Judge Kavanaugh noted, once asked the Supreme Court for advice (about a British brig, the Little Sarah, that we’d seized).

The court wrote Washington, who’d presided at the 1787 convention that framed the Constitution and who’d signed the parchment, a letter telling him they couldn’t oblige. That’s because what the Constitution empowers the court to decide is actual cases or controversies.

Which is why — here’s hope for even the Democrats — not even presidents can be sure of what the judges they nominate will do once they’re seated for life.

This column first appeared in the New York Post.