Rep. Adam B. Schiff (D-Calif.) is the chairman of the House Permanent Select Committee on Intelligence.

Most Americans remember Watergate as a scandal involving the burglary of the Democratic National Committee headquarters and President Richard M. Nixon’s coverup of that crime. But during the course of the subsequent investigation, an even broader range of presidential misconduct was revealed. Nixon maintained a secret enemies list, some of whom were the subject of extraordinary abuses, including the use of the IRS to target their tax filings and the FBI to monitor their phones.

Nixon’s abuse of the Justice Department led to strict rules to govern FBI investigations and insulate them from White House interference, so that extraordinary investigative practices could only be deployed when justified in the most serious of cases.

The rules established after Watergate to ensure the independence of the Justice Department served our nation well for half a century, until another president shattered them.

Donald Trump had his own enemies list, which included members of the media, elected officials and congressional staff. But while Nixon’s list was held in private, Trump was proud to declare his enemies on Twitter, at rallies and during interviews.

And Trump made no secret of his demand that the Justice Department investigate his opponents, openly demanding his attorneys general go after any number of people. Including — quite frequently — me.

Over his four years in office, Trump baselessly accused me of treason, of leaking classified information, of engaging in unspecified corruption and other offenses. He said I should be investigated and prosecuted, and that someone needed to “do something” about me.

Last month, I learned that Apple had been served a subpoena by the Justice Department in 2018 seeking records from more than a dozen accounts belonging to two members of Congress, committee staff and even family members — one of whom was a minor. There is a lot we don’t know, including how the department came to seek those records and whether prosecutors understood what records they were requesting. We still don’t know whether only Democrats were the subjects of these requests or whether the investigation was properly predicated. The department has yet to explain.

The investigation reportedly began under then-Attorney General Jeff Sessions and his deputy, Rod J. Rosenstein, and was continued under Attorney General William P. Barr. Leak investigations, particularly those involving subpoenas on members of the media, are extraordinarily sensitive and require approval from top DOJ officials. Subpoenaing the records of members of Congress in connection with such an investigation may be unprecedented, since our constitutional doctrine of the separation of powers militates against the executive branch taking such action. In this case, prosecutors also repeatedly sought gag orders so that the media and Congress would not find out. That all three top Justice Department officials at the time now deny any knowledge of the matter strains credulity.

We cannot accept these assertions at face value. Sessions made claims during his confirmation hearing that were not borne out by the facts. Barr has a well-documented history of dissembling, including under oath. Barr willfully misrepresented the Mueller report even as he withheld it and claimed not to know of Mueller’s objections to his “summary” of that report when he did. Barr also made false representations to the court about the process of reaching his conclusion that Trump committed no prosecutable offense — two federal judges have now rebuked him for his lack of candor.

And to the department’s lasting detriment, Barr repeatedly put the DOJ into service as Trump’s personal law firm, reducing the sentencing recommendation of a Trump crony who lied for the president and dismissing the case against another Trump associate who pleaded guilty to perjury. Barr then abused his office further by ordering the investigation of those who had investigated the president.

The Biden Justice Department has taken the right first steps. Attorney General Merrick Garland has asked the inspector general to investigate both the subpoenas affecting members of Congress and those served on the media. But it will also be essential for the attorney general to examine the full extent to which the department lost its independence over the past four years. We must establish new and stronger laws and policies to protect the agency from presidential and political interference in the future. Given Garland’s long history with the department, I have every confidence that he will do so.

But Congress has an important job to do here, too. We must conduct our own vigorous oversight, into former top officials’ knowledge or participation in these abuses of power and any other politically motivated decisions made by the department. And at a minimum, we must urgently pass reforms to prevent the abuse of powers we saw under Trump from ever happening again. The Protecting Our Democracy Act, a package of reforms designed by House Democrats that I introduced last year, contains new safeguards designed to strengthen the department’s independence from the White House and improve other vital checks on executive power.

The credibility of our justice system — and the very health of our democracy itself — is dependent on the steps we take now to ensure that the Justice Department represents the interests of the people and not the whims of any particular president.

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