FUSHUN, China — Some national heroes are born in the crucible of war. Others have far less dramatic origins.

So it was in the summer of 1962, when a soldier at this army base in northeast China reversed his truck into a telephone pole, sending it crashing onto the head of a 22-year-old comrade. The young man died, but his short life provided Communist Party propagandists with a perfect icon: Lei Feng, industrious, generous and irresistibly impish, China’s most endearing soldier, the sort of fellow who would darn his comrades’ socks and skip a meal so others might eat.

In urging people to “Learn from Lei Feng” a year after his death, Mao Zedong sought to imbue China’s youth with a passion for self-sacrifice and patriotism — and perhaps distract them from the hunger pangs of famine that followed his disastrous effort to rapidly industrialize in the Great Leap Forward.

But the party’s efforts to resuscitate the spirit of Lei Feng on the 50th anniversary of his death have exposed the limits of old school propaganda in the age of the Internet. The campaign, which culminated Monday with the annual “Learn From Lei Feng Day,” has provoked a fresh round of public cynicism about a ruling party that is struggling to cultivate a sense of legitimacy....