As China grapples with ongoing trade tensions with the United States and a slowing economy, many come to the lake in search of an emotional lift. They sing patriotic songs, recite Mr. Xi’s slogans about the “Chinese dream” and reminisce about revolutionary heroes.

“We want to show our gratitude to the party,” Mr. Liu said, “and to remember that China can only be strong with a strong party.”

The experience of the visit culminates at a 161-foot-long wall emblazoned with the party’s hammer-and-sickle flag, where visitors clench their fists and recite an oath of loyalty to the party, a communist ritual that has come back into fashion under Mr. Xi, who also serves as the party’s chairman.

In 1921, Mao Zedong and a small group of revolutionaries held the party’s first congress on a boat in the middle of the lake, after the police chased them out of Shanghai, about 60 miles northeast. Across China, the so-called “red boat” is well known.

At the museum at the lake, which started construction when Mr. Xi was the top party official here in Zhejiang Province, a selective retelling of party history is on display.

Inside, there are exhibitions about China’s “century of national humiliation” at the hands of foreign powers, the spread of Marxism in China and Mao’s founding of the People’s Republic in 1949.

A glittering display on the top floor is devoted to Mr. Xi, China’s most influential leader since Mao. His speeches play on loop and his slogans are plastered across the walls, including one that says, “Lead the great renewal of the Chinese nation.”