A month after the 2016 election, the stock trader Andrew Left went out to the Madison Club in La Quinta, Calif., to lick his wounds and play golf. The way Left invests, he can make a killing in a bear market while everyone else on Wall Street suffers. But in December, even dubious stocks were rising, lifted by the promise of incipient deregulation. Reading the news on his phone between holes, Left happened upon an interview with President-elect Donald Trump, the purveyor of all this optimism, in Time magazine. “I’m going to bring down drug prices,” Trump said. “I don’t like what’s happened with drug prices.” Left hurried back to the clubhouse and gave his ticket to the valet.