To allow students to block the city center and impede traffic shows weakness. Hong Kong's reputation as a financial center and tourist attraction will suffer. And Beijing cannot permit this to go on too long without risking supportive protests erupting on the mainland. Nor can the students be allowed to force Hong Kong to give up Beijing's veto of candidates. To capitulate would expose President Xi Jinping as a leader who can be broken by street action. To permit that perception would imperil Xi's standing with Beijing's hard-liners, and potentially the regime itself.