In 2011, Donald Trump spoke before an audience of about a thousand in Las Vegas, teasing a prospective, if fanciful, presidential run. Halfway through a rant over Middle East policy and oil prices, he digressed for a moment to discuss trade with Asia: China, I said the other day — very, very hard to buy anything, outside of China. Certain other countries also, but China’s, you know, the one. And somebody said, “What would you do? What could you do?” So easy. I drop a 25 percent tax on China [applause]. And you know, I said to somebody that it’s really the messenger. The messenger is important. I could have one man say, [falsetto] “We’re going to tax you 25 percent .” And I could say another [ sic ]: “Listen, you motherfuckers, we’re going to tax you 25 percent!” Since long before he became President, Trump has flip-flopped constantly on the standard presidential topics, from the Middle East to health care to abortion.…