Researchers at the University of Toronto showed how hackers could use artificial intelligence to create a program that could target any known flaw in the world’s computers.

Mr. Platner, the likely Democratic nominee for Senate in Maine, met in Washington with several senators. Chuck Schumer, the minority leader, dodged questions about his confidence in Mr. Platner.

Over the past two decades, Iran repeatedly threatened to close down the waterway. President Trump underestimated Iran’s ability to do so.