Wall Street traders know what to expect from Donald Trump’s White House return: policy shifts rolled out in late night social-media posts, threats to trading partners, and plenty of market volatility.

U.S. stock indexes are rallying toward the close of their best week in two months. The S&P 500 rose 1.1% Friday.

The only danger, from Wall Street’s perspective, is that the Trump team’s MAGA instincts and chaotic approach prevent a deregulatory boom. One appointment is emblematic of the coming shift. Gary Gensler,