The regime of Supreme Leader Ayatollah Ali Khamenei has weathered bouts of protests many times, but demonstrations that began two weeks ago are spreading — by some accounts, hundreds of thousands of people defied authorities’ threats and a brutal crackdown to take to the streets over the weekend, from the capital Tehran to dozens of other cities across the nation of 90 million. They are being cheered on by President Donald Trump, fresh off the capture of Venezuela’s Nicolas Maduro, and the US leader has in recent days repeatedly threatened to strike Iran, suggesting that America is back in the regime change business.