China’s strongman leader,Xi Jinping, is hoping that a crackdown on dissent and corruption will shore up the party’s rule. He is determined to avoid becoming theMikhail Gorbachev of China, presiding over the party’s collapse. But instead of being the antithesis of Mr. Gorbachev, Mr. Xi may well wind up having the same effect. His despotism is severely stressing China’s system and society—and bringing it closer to a breaking point.