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The stock market is still up more than 20 percent since Nov. 8, 2016, the day Mr. Trump won the White House — a roller-coaster ride driven in part by expectations about what a Trump presidency could bring to Washington.
At first, the prospect of Republicans controlling the White House and both houses of Congress thrilled investors. They anticipated a wave of regulatory rollbacks and the slashing of corporate and personal tax rates. Many of those dreams have been realized, culminating in Mr. Trump signing a huge tax cut into law in December. When the S.&P. 500 notched its high-water mark of 2872.87 on Jan. 26, it represented a roughly 325 percent increase since the bull market began in March 2009.
But since February, a toxic stew of factors — many but certainly not all of them emanating from Washington — has polluted what had been the market’s placidly rising waters. And there’s little prospect of the messes dissipating anytime soon.
First there was the risk that the economy might be growing too fast, which could prompt central banks to hike interest rates sooner than expected. Then there was the risk of a trade war ignited by the White House imposing tariffs on certain products, an action that quickly prompted countries like China to erect trade barriers of their own. Next came the threat of a government crackdown on technology companies, after revelations of their misuse of customer data.
Monday’s dose of unnerving news was a presidential tweet aimed at Amazon, which Mr. Trump accused of hurting the United States Postal Service. Mr. Trump’s feud with the company has been going on sporadically since before he became president, but the onslaught has accelerated lately. On Monday, Mr. Trump tweeted that the Post Office loses money by working with Amazon “and this will be changed.”
