Trump's stock market recoil

American presidents cannot help but pay attention to the stock market. The reasons should be obvious: While many observers dismiss the market's performance as being largely divorced from the country's economic fundamentals, it's undeniable that over the long run, at least, the markets can tell a meaningful story about the U.S. economy. And fairly or not, presidents take credit or receive blame for economic and market performance on their watch. The thing is, stock market performance really...