Makan Delrahim, the head of the Justice Department’s antitrust division, is paid by taxpayers to prevent corporate mergers that damage the public interest. Instead of doing this important police work, however, Mr. Delrahim has chosen to cast himself as a deal maker.

The Times reported on Thursday that Mr. Delrahim worked assiduously this past summer to clear the way for the merger of two rival mobile phone companies, T-Mobile and Sprint, by helping to arrange for the two companies to sell some assets to a third company, Dish. Mr. Delrahim behaved like a man who wanted to make a deal. In text messages, which were disclosed as part of a related court case, he repeatedly coaxed and cajoled executives at the three companies, as well as federal officials who had the ability to block the merger.

Mr. Delrahim has cast his actions as a defense of the public interest. In announcing that the Justice Department had approved the merger in July, he said that he had been prepared to go to court to block the merger had Dish not participated in the agreement. The asset sales are intended to allow Dish to emerge as a viable new mobile phone company, filling the void when Sprint departs the marketplace.

But Mr. Delrahim was negotiating with himself. His campaign to secure Dish’s participation amounted to a concerted effort to satisfy his own objections to the proposed deal. Rather than defending the public interest, he was working to defend T-Mobile’s interests.