Officials at the White House and the Justice Department insist they haven’t discussed the case with one another. They also say that political considerations have played no role in the department’s review. But it’s interesting, and to some people suspicious, that the chief of the Antitrust Division, Makan Delrahim, has changed his mind about the deal. In October 2016, he said he did not see a “major antitrust problem” with an AT&T-Time Warner marriage. Now he does, and he supports the divestiture of Turner and CNN. Reasonable people are bound to ask if he changed his mind because economists and lawyers at the Antitrust Division persuaded him, or because he was influenced by Mr. Trump’s tweets and public statements.

Justly or not, Mr. Delrahim suffers from the same suspicions that attach to just about all of Mr. Trump’s appointees. By firing a director of the F.B.I., by demanding that the Justice Department investigate his political opponents and by attacking judges, Mr. Trump, unlike other presidents of the modern era, has shown little but contempt for the independent, honest judgment of government departments and agencies. In a more insidious fashion, he has undermined the integrity of public service by appointing people to important jobs who have glaring conflicts of interest. He has stacked the Environmental Protection Agency with officials who have long ties to the fossil fuel and chemical industries; a similar bias infects the Interior Department.

This week, the president nominated a former pharmaceutical industry executive, Alex Azar, who led a company that repeatedly raised the price of important drugs like insulin, to head the Department of Health and Human Services.

Mr. Delrahim could well be an exception. But he has a lot to prove. For starters, his division needs to build a strong legal case against the AT&T-Time Warner deal. He will also need to explain why the Justice Department, instead of requiring a divestiture, could not use the same approach it did in 2011 when it allowed Comcast, a cable company, buy NBCUniversal, a media business, as long as the company agreed to treat other cable companies and internet streaming firms like Netflix fairly.

Further, to show that his views on this deal are more than politically expedient, Mr. Delrahim needs to be just as tough on other mega-mergers that come before him. He will have no credibility if he takes an aggressive stand against AT&T-Time Warner but then goes easy on deals involving companies owned or controlled by conservative tycoons, like the pending Sinclair Broadcast Group acquisition of Tribune Media and any deals made by 21st Century Fox, which has reportedly had talks to sell assets to Disney. Mr. Trump’s appointee to head the Federal Communications Commission, Ajit Pai, has, in fact, changed rules to help Sinclair get bigger, and also seeks to make it easier for media companies to own multiple news outlets in the same market.