Now that special counsel Robert Mueller has completed his investigation, it is tempting to breathe a sigh of relief and assume that our long national nightmare is over. Resist the temptation, the assumption is false.

We are not close to the end. Not by a long shot.

In fact, I believe the last two years, as traumatic as they were, will prove to be the easier part of the nightmare, because Mueller dealt only with whether Donald Trump’s 2016 campaign conspired with Russia to swing the election. Based on what we know so far, especially that no more indictments are coming, it appears that Mueller’s answer is no, there was no collusion or obstruction of justice.

If true, this is an enormous vindication for Trump, who insisted all along that he had done nothing wrong. Supporters were understandably in a celebratory mood, with some saying on Twitter that it felt like 2016 election night all over again.

Meanwhile, Trump’s vindication is a devastating rebuke to Democrats and their media handmaidens, all of whom insisted his guilt was guaranteed. Their legacy is that they ruined their own credibility, and their continuing efforts to destroy him by innuendo and investigation can only add to their disgrace.

For them, too, Friday night was like a repeat of Trump’s election victory.

Oh, to be a fly on the wall at Hillary Clinton’s house.

But even as we learn the details of what Mueller found, there remains a giant black hole about the very origins of the FBI investigation that led to his appointment in the first place.

It is astonishing, for example, that at this late date, we still do not know what evidence the disgraced James Comey and his FBI had to open the original probe in the summer of 2016, and whether there was anything other than the fatally tainted Russian dossier.

Nor do we know of any compelling reason why Deputy Attorney General Rod Rosenstein later decided a special counsel was necessary to get to the bottom of the swirling accusations of collusion that started during the campaign and mushroomed after Trump’s upset victory.

Recall that Rosenstein effectively urged that Comey be fired in May 2017, then eight days later, mysteriously decided the action warranted an investigation from outside the Justice Department.

Rosenstein’s conflicts of interest are appalling and the Mueller appointment cast a cloud over the presidency and fueled conspiracy theories about the legitimacy of Trump’s election. The true impact is incalculable, but we know those claims led to the resistance movement and that Mueller was used by some Dems to justify boycotting the State of the Union speech and refusing to support any of Trump’s appointments or legislation.

The reckless talk of impeachment also surely had some negative effect on the behavior of our allies and adversaries.

Now, with Mueller finished, it is time to give equal attention to the other side of the story, of how we got here. The questions can be boiled down to two.

Was the initial decision to investigate Trump’s campaign an honest mistake by the Obama administration? Or was it an attempt to rig the election in favor of Clinton, and when that failed, overthrow a duly elected president?

Those outstanding issues are as worthy of complete answers as those that Mueller investigated. In addition to knowing whether there was an improper relationship between a candidate and a foreign power, Americans also deserve to know what was going on inside their own government and whether it was simply incompetent or thoroughly corrupt, or some combination of the two.

Put another way, what did President Barack Obama and his administration do, and why did they do it?

The task of finding out falls to the new attorney general, William Barr. He will have his plate full in the coming days deciding how much of the Mueller report can legally be made public and explaining his decision to Congress.

I don’t underestimate the importance of the issue, but Barr must not be consumed by it. Indeed, he needs to deliver on another promise he made during his Senate confirmation hearings, where he said he was alarmed by the demonstrated bias against Trump by top FBI agents such as Peter Strzok and Lisa Page, and suggested he was not satisfied the FBI and the Justice Department had been fully held accountable.

The key sequence involved questions from the Judiciary panel’s Republican chairman, Sen. Lindsey Graham of South Carolina.

Graham: “Do you promise me as attorney general — if you get this job — to look and see what happened in 2016?”

“Yes, Mr. Chairman,” Barr replied.

“How do these statements sit with you?” Graham asked, referring to the Page and Strzok texts showing they hated Trump and wanted Clinton to win the election.

“I was shocked when I saw them,” Barr answered.

Graham: “Please get to the bottom of it … we’re relying on you to clean this place up.”

Getting to the bottom of it would mean a criminal probe of Comey and his former deputy, Andrew McCabe, along with others in the leadership ranks of the FBI. Did they, as it appears, fail to disclose to the court that Clinton’s team commissioned and paid for the Russian dossier and that its allegations were unverified when they sought approval to spy on the Trump campaign?

If the answers are yes, they may have committed felonies, as did those who authorized any misleading court applications, including Rosenstein.

A criminal probe would also mean uncovering any role played by the reprehensible John Brennan, then head of the CIA, James Clapper, head of national intelligence, and Susan Rice, Obama’s national security adviser, in creating the FBI probe and leaking classified information.

Among the questions they need to be asked under oath is, did you have any role in spreading the Clinton-funded dossier to the media? Did you leak the names of Trump associates picked up on wiretaps?

In addition, of course, there are also fundamental doubts about the integrity of the FBI’s investigation of Clinton’s handling of classified emails. The doubts include what role, if any, Loretta Lynch, then the attorney general, and others in the Obama administration played in the suspect exoneration of Clinton.

Because there are so many questions about the Clinton case and the origins of the Trump probe, the best and only fair solution is for Barr to appoint a new special counsel. Given the critical issues involved, even-handedness demands a prober free of conflicts with the former officials cited.

Unlike the Mueller probe, which ranged too far and took too long, this investigation should be focused on credible allegations against Clinton and top officials of the Obama administration. And it must be completed before the 2020 election so voters can know the whole story of what happened in 2016 and the early days of the Trump presidency before they vote again.

Then, and only then, can we say that our long national nightmare is over.