The decision to abandon the deal “highlights one of the possible implications of more aggressive enforcement” as Mr. Biden makes good on campaign promises to be tough on companies, said A. Douglas Melamed, a law professor at Stanford University and former acting chief of the Department of Justice’s antitrust division.

The F.T.C. and the Justice Department are likely to look for ways to have an impact without being subject to judicial review, Mr. Melamed said, and one way to do that is by challenging mergers in general, whether or not a case has a good chance of winning.

“The risk and time delays of a merger challenge often cause the parties to abandon a deal even if the government’s case is weak,” he said.