On Monday, two days before the Senate hearing to consider Todd Blanche’s nomination to become the nation’s chief law enforcement official, a federal judge strongly suggested that he may not even be fit to practice law.

Earlier this year, Mr. Blanche agreed to a settlement that resulted in tax audit immunity for President Trump and his family as well as a potential $1.8 billion payout fund controlled by his administration. It was an inside deal: Mr. Trump the citizen was on one side of the negotiation, while the Internal Revenue Service, which he oversees, was on the other. Judge Kathleen Williams of the Southern District of Florida said in her ruling on Monday that she was “extremely troubled” by Mr. Blanche’s behavior. It was so egregious that she referred his actions to the New York State Bar Association for potential disciplinary action, including disbarment.

The scheme was one of many ways that Mr. Blanche, who was previously Mr. Trump’s personal lawyer and now serves as acting attorney general, has placed the interests of his former client above those of the country. It is yet another reason that senators of both parties should reject the president’s demand that Mr. Blanche be confirmed to lead the Department of Justice.

Of all the powers Americans give their government, none can curtail personal liberty like those of the Department of Justice, and this editorial board has listed the ways Mr. Blanche has abused that authority. He has celebrated the Jan. 6 rioters. He has misled Congress under oath. He has said it is Mr. Trump’s “right,” and “indeed it is his duty,” to use the department to investigate people he “has had issues with.”

Most Republican senators on the Judiciary Committee nonetheless appear likely to vote for Mr. Blanche. Yet at least two — John Cornyn of Texas and Thom Tillis of North Carolina — have already raised questions about the nomination. Mr. Cornyn and Mr. Tillis are in their final terms in office, partly because Mr. Trump considered them insufficiently subservient to him. They should have the decency, patriotism and self-respect to vote against Mr. Blanche.

To understand why Mr. Blanche poses such a threat to America’s system of justice, look at how sharply he and Mr. Trump have strayed from traditional restraints on the use of law enforcement powers.

Mr. Blanche’s relationship with the president stems from his role as a private lawyer. Over the past decade, Mr. Blanche first represented Trump allies like Paul Manafort before joining the team that defended Mr. Trump over his hush-money payments to the actress Stormy Daniels. After Mr. Trump won the election in 2024, he chose Mr. Blanche to be deputy attorney general.

Ethical guidelines exist to prevent government lawyers who previously were in private practice from using their offices to aid their former clients rather than their current one, the people of the United States. In Judge Williams’s suggestion that Mr. Blanche be a candidate for punishment, she cited these conflict-of-interest guidelines.

He has brazenly defied them at the Justice Department over the past year and a half. He has presided over the frivolous indictments of the former F.B.I. director James Comey and the investigations of the former C.I.A. director John Brennan and the former White House aide Cassidy Hutchinson, all perceived enemies of the president. The cases have gained no traction in the courts.

Mr. Blanche has also mounted an onslaught against the news media, attempting to undermine the First Amendment. Under his watch, the F.B.I. raided the home of a Washington Post reporter and issued multiple subpoenas against news organizations, including The Wall Street Journal. Last week, the F.B.I. director, Kash Patel, who works for Mr. Blanche, went to the White House to oversee an investigation that led to the subpoenaing of five New York Times reporters who broke the news that Mr. Trump’s new version of Air Force One had security flaws.

These acts represent an appalling politicization of law enforcement. Mr. Blanche has helped Mr. Trump violate decades of bipartisan tradition and use the Justice Department as an instrument of personal power.

If Mr. Blanche is confirmed, the problems are likely to worsen. Mr. Trump has repeatedly indicated an interest in interfering with this year’s midterm elections. He continues to lie about his 2020 defeat, and his administration, including Mr. Blanche, has investigated election officials who have done nothing wrong. There is every reason to worry that Mr. Blanche might use the powers of the Justice Department to intimidate voters or interfere with ballot counting this fall.

Congressional Republicans have shown that they can exert influence over Mr. Trump. It often takes only a modest number of them. Working with Democrats, Republicans ended Matt Gaetz’s effort to become attorney general after the 2024 election. They forced Mr. Trump’s Justice Department last year to release the Epstein files. They forced Mr. Trump and Mr. Blanche to retreat, at least for now, from their planned $1.8 billion slush fund that would have benefited Jan. 6 rioters.

This week, Republicans, starting with Mr. Cornyn and Mr. Tillis, have an opportunity to prevent Mr. Blanche from doing further damage. Americans can be grateful that the Constitution still provides robust protections of personal liberty, but its words mean little if members of Congress do not stand up to dangerous presidential power grabs.