BEIJING — When Xi Jinping strode out in the Great Hall of the People five years ago as China’s new leader, his tight smile barely hid the atmosphere of smoldering crisis.

The Communist Party elite had been battered by infighting and scandals involving power grabs, bribery and even murder. Military commanders and state security chieftains — the guardians of one-party rule — had grown grossly corrupt. Critics openly accused Mr. Xi’s predecessor, Hu Jintao, of dithering as popular ire spread.

On Wednesday, Mr. Xi opened another Communist Party congress, this time as the nation’s most powerful leader in decades, all but certain to receive a second five-year term. And after spending his first term tightening control on society, he is expected to enshrine his authoritarian vision for revitalizing the party — and perhaps position himself as indispensable to its survival.

“Currently, conditions domestically and abroad are undergoing deep and complicated changes,” Mr. Xi told some 2,300 party delegates and other dignitaries assembled in the Great Hall. “Our country is in an important period of strategic opportunity in its development,” he said in a calm, steady voice. “The outlook is extremely bright; the challenges are also extremely grim.”