“If Xi goes for broke and breaks precedent by not preparing for an orderly and peaceful succession, he is putting a target on his back and risking a backlash from other ambitious politicians,” said Susan L. Shirk, the chairwoman of the 21st Century China Center at the University of California, San Diego.

“By taking such a risk, he shows himself to be more like Mao than we originally thought — he demonstrates his power by overturning institutions,” she added.

Mr. Xi’s authoritarian approach was meant to bring faster policymaking after years of stagnation under his predecessor, Hu Jintao. Instead, critics say, the concentration of power in one man’s hands has created its own bottlenecks, with officials unsure how to execute policies or afraid to deviate from top-down demands.

The lack of a potential successor could be seen as a sign that Mr. Xi intends to dominate beyond this next five-year term, which ends in 2023, either by staying in office or behind the scenes. He may also want more time to test possible successors, while avoiding lame duck status with an heir waiting in the wings.

In a possible nod to concerns about Mr. Xi amassing too much power, most of the five new Standing Committee members were not longtime associates of his, though all have worked with him in some capacity. Premier Li Keqiang, the only holdover from the outgoing committee besides Mr. Xi, was once seen as a possible rival to lead the country.

Among the new members were Wang Yang, a vice premier who promoted himself as a can-do reformer while party chief of Guangdong Province in southern China, and Han Zheng, a former mayor of Shanghai who is credited with guiding that city’s emergence as China’s glittering financial and business capital. Neither had a long history of working closely with Mr. Xi before he became president in 2012.