There exists today no vaccine for the coronavirus now engulfing China. That is a challenge for President Xi Jinping as he struggles to contain it. But the spread of the coronavirus has revealed a truth that poses a much greater risk to Mr. Xi: There is no cure for Chinese communism except the collapse of the party.

The more Mr. Xi pursues his authoritarian agenda, the more distrust he will sow at home and abroad. Far from transforming Beijing into the world’s leading superpower, his policies will instead keep China from taking...