BEIJING  President Hu Jintao of China returned home this weekend after a trip intended to repair relations with the United States. But the next time the White House marches out the honor guard and polishes the crystal for a Chinese leader, it is unlikely to be for Mr. Hu.

Following a secretive succession plan sketched out years ago, Mr. Hu has already begun preparing for his departure from power, passing the baton to his presumed successor, a former provincial leader named Xi Jinping, now China’s vice president. While Mr. Xi is expected to formally take the reins next year in China, the world’s second-largest economy and fastest-modernizing military power, he remains a cipher to most people, even in China.

But an extended look at Mr. Xi’s past, taken from wide-ranging interviews and official Chinese publications, shows that his rise has been built on a combination of political acumen, family connections and ideological dexterity. Like the country he will run, he has nimbly maintained the primacy of the Communist Party, while making economic growth the party’s main business.

There is little in his record to suggest that he intends to steer China in a sharply different direction. But some political observers also say that he may have broader support within the party than Mr. Hu, which could give him more leeway to experiment with new ideas. At the same time, there is uncertainty about how he may wield authority in a system where power has grown increasingly diffuse. Mr. Xi also has deeper military ties than his two predecessors, Mr. Hu and Jiang Zemin, had when they took the helm.