The review of AT&T’s acquisition of Time Warner has drawn speculation because of promises Mr. Trump made on the campaign trail to block the deal. Mr. Trump’s disdain for news coverage by CNN, which is owned by Time Warner, has raised questions over whether the president may try to influence the deal. Jeff Sessions, Mr. Trump’s attorney general, has promised to block any political influence on Justice Department decisions.

Mr. Delrahim, whose nomination will go before the Senate for confirmation, is expected to take a more free-market approach to his job of antitrust enforcement, according to analysts. His style is expected to be in line with mainstream Republicans.

The White House did not immediately respond to a request for comment on Mr. Delrahim’s appointment.

He has deep experience in government as the former deputy assistant attorney general for antitrust during the George W. Bush administration. He previously was an antitrust attorney and partner at Brownstein Hyatt Farber Schreck in Los Angeles.

Mr. Delrahim also has a background in lobbying that could create conflicts of interest in merger reviews and antitrust enforcement actions. In 2016, he was registered as a lobbyist for Blue Cross Blue Shield, Caesars Entertainment and Qualcomm, according to the Center for Responsive Politics’ OpenSecrets website. Seven years ago, he was a registered lobbyist for Comcast.

Mr. Delrahim left private law to join the Trump administration in January. He had been tasked to work on the Senate confirmation of Judge Neil M. Gorsuch to the Supreme Court.