THINGS CHANGE fast in Donald Trump’s America. Before the strike on Iran, public opinion showed Americans overwhelmingly opposed to attacking the country. Polling for The Economist by YouGov last week showed that 60% of American adults opposed military involvement against just 16% who supported it. Much of that is due to the memory of the Iraq and Afghanistan wars, which few Americans think were worth their cost in blood and treasure. In the immediate aftermath of the attack, public opinion appears to be polarising along the familiar partisan lines—as Republicans rally around the flag (and against the Democrats). In fact, YouGov’s polling for us shows that this is already happening (see chart).