One of the most prominent supporters of Britain’s withdrawal from the European Union, Mr. Johnson made clear on Tuesday that he would push for Brexit by the Oct. 31 deadline, even if there is no deal in place. We answered some questions about how the process might play out.

News analysis: President Trump referred to Mr. Johnson as “Britain Trump” on Tuesday, and is encou raging the new leader to push on with Brexit. But Mr. Johnson could be constrained by the complexities of British politics and his establishment background, our correspondents write.

Another angle: The famously rumpled Mr. Johnson has upended the rules of what leadership should look like, our fashion critic writes. He also brings a chaotic personal life to 10 Downing Street.

Big tech faces antitrust review

The Justice Department said on Tuesday that it would examine how internet giants had accumulated market power, the clearest sign yet that the arguments that helped shield the tech giants from competition scrutiny are eroding.

Similar inquiries are underway in Congress and at the Federal Trade Commission.

The Justice Department didn’t name specific companies, but said it would look into concerns about search, social media and retail services, presumably a warning to Google, Facebook and Amazon.