(Sina Weibo)

On May 1, 1989, one month before Chinese troops killed hundreds of protesters in and around Tiananmen Square in Beijing, the general secretary of the Chinese Communist Party, Zhao Zhiyang, made his case for compromise in a private session of the Politburo. "Democracy is a worldwide trend," he said, according to former Washington Post reporter Philip Pan's excellent book "Out of Mao's Shadow." Zhao went on: "If the party does not hold up the banner of democracy in our country, someone else will, and we will lose out. I think we should grab the lead on this and not be pushed along grudgingly."

Zhao lost out, as did the protesters. But Chinese leaders were not content to simply shut down the protesters and fire Zhao. They, and the movement for political liberalization they represented, were considered so dangerous that they had to be forgotten completely. Zhao was banished to house arrest, where he lived out his years in forced isolation. As for the protests and massacre in Beijing, they never happened. Discussion of the events on June 4 remain so taboo and so heavily censored that, when people do dare to discuss them, they often refer to "May 35th."

This year, the censorship around Tiananmen's anniversary is reaching new heights. The Wall Street Journal's Josh Chin reports that Chinese social media sites are not just blocking Tiananmen-related search terms but even oblique, tertiary references. Chinese Web users can't search for the phrase "black shirt," for example, presumably because a Chinese activist named Hu Jia had called on people to wear black T-shirts in a subtle nod to the anniversary.

Even mentions of yellow rubber duckies are blocked on the Chinese Web. Not because they're a potent or politically charged symbol of the anniversary but because some anonymous person in China, referencing the giant rubber duck currently floating in Hong Kong's Victoria Harbor, posted an image on social media of the famous "tank man" photo with giant rubber ducks replacing the tanks. It probably took about 20 minutes in Photoshop, but it was enough to get not just the image deleted from Weibo but searches for all things yellow rubber duck-related blocked.

You could be forgiven for seeing the extent of the censorship as a bit absurd; are rubber duckies really so dangerous to one of the most entrenched single-party states on Earth? But the censorship isn't just about preventing even the slightest hint of possible 1989-style unrest – although that's certainly part of it. It's also about delaying the conversation that Zhao (and, in their own way, the protesters) tried to start.

"Can a one-party system ensure the development of democracy?" Zhao asked Mikhail Gorbachev when the Soviet leader visited Beijing shortly before the crackdown. "Can it implement effective control over negative phenomena and fight the corruption in party and government institutions?" Can China's Communist Party, in other words, continue resisting change and still survive?

Today's Communist Party leaders are no dummies; they give every indication of wondering about these very same questions today. And they have, in fact, slowly reformed the political system, which is more open today than it was in 1989, though not as open as Zhao wanted. Still, Chinese leaders such as Hu Jintao, who led the country and the party from 2002 to 2012, did much more to kick that can down the road, to delay the party's dilemma over its maintaining single-party power without risking more of 1989's instability, than he did to address or resolve it. And that's still the status quo.

This is a problem that China's leaders have addressed repeatedly since 1989 and, as with the almost laughably broad censorship of rubber ducks for the marginal association with Tiananmen, they have consistently avoided the issue. Then-Secretary of State Hillary Clinton, in a 2011 interview with the Atlantic's Jeffrey Goldberg, channeled the view of many so-called "China bears," or skeptics of the Communist Party's long-term viability. Goldberg noted that Chinese authorities had appeared frightened of the "Arab Spring" uprisings half a world away. "Well, they are," Clinton said. "They're worried, and they are trying to stop history, which is a fool's errand. They cannot do it. But they're going to hold it off as long as possible."

Maybe Clinton is right that the Communist Party can't "stop history" and maybe she's wrong. Maybe Chinese leaders will one day try to answer Zhao's questions from May 1989. But, for the time being, they would repress the memory of Tiananmen than try to reconcile with that dark day in Chinese history.