The twilight of China's Communist Party

“I can't give you a date when it will fall, but China's Communist Party has entered its endgame.” So says one of America's most experienced China watchers to a small table of foreign diplomats at a private dinner in Washington, D.C. The pessimism from someone with deep connections to the Chinese government is notable. Washington should start paying attention if it wishes to avoid being surprised by political earthquakes in the world's second-largest economy.

The China scholar at my table is no conservative. Nor are the handful of other experts. Each has decades of experience, extensive ties to Chinese officials and is a regular visitor to the mainland. No one contradicts the scholar's statement. Instead there is general agreement.

“I've never seen Chinese so fearful, at least not since Tiananmen,” another expert adds, referring to the 1989 massacre of pro-democracy student demonstrators in the heart of Beijing. When prodded for specifics, he mentions increased surveillance, the fear of being investigated and increased arrests.

Just as there is no dissent from these views, there is unanimity on the cause of the new atmosphere of fear: President Xi Jinping .

In just two years, Mr. Xi has become the most powerful Chinese leader since at least Deng Xiaoping, and perhaps even since Mao Zedong. Some longtime experts talk about the possibility of something approaching one-man rule in Beijing, anathema since the excesses leading up to Mao's death in 1976. Others argue that collective leadership is alive and well, but the party is indeed tightening its grip on Chinese society.

The clearest manifestation of Mr. Xi's power is the unprecedented crackdown on corruption. The sensational corruption and murder scandal of former Politburo star Bo Xilai in 2012-13 was just the starting point in a campaign that has also snared Zhou Yongkang, the former head of the powerful security committee and an inner member of the Standing Committee. Now the former chief of staff to ex-President Hu Jintao is also being investigated. State media report that 180,000 party officials have been “disciplined.”

While Mr. Xi clearly is attempting to restore the party's credibility with cynical and disenchanted Chinese, he is also sending messages about his strength and the reach of the Party throughout Chinese society. Faced with an economic slowdown that may impact the living standards of the middle class, Mr. Xi is short-circuiting any potential large-scale unrest. More worrisome, he may be gathering unprecedented power—but perhaps it is more the flaring of a candle before it gutters.

If the party really is in its endgame, then neither Mr. Xi's dramatic anticorruption campaign nor his reform program will mean much, at least in the long run. Cynicism in China is at an all-time high. The elite hold foreign passports for their families, and wealth is being transferred offshore through real estate holdings and other means. A maturing Chinese economy means an economic slowdown in any case, but a more sustained downturn would exacerbate the tensions that remain just under the surface. Nor can one discount the possibility that the knives will come out for Mr. Xi, leading to internecine war within the party.

It is hard, if not impossible, to imagine a post-Communist China. The country's democratic and liberal voices have been suppressed for decades, and the extent of public sympathy for their cause is ultimately unknowable. A period of increasing unrest and internal disruption would undoubtedly follow any loss of power by the Communist Party.

If all this is accurate, then what should the West do? “Get outside the Fourth Ring Road,” the first specialist says, referring to the center of government power in Beijing. Western diplomats, scholars and NGOs are too isolated from the Chinese people. Greater engagement with China's various voices, from farmers to educators to liberal activists, is the only responsible approach for the long run.

Also build links to marginalized Chinese. “When was the last time you heard Washington criticize Beijing's human-rights record or labor relations?” the same scholar asks. It's time to show that the West has a moral stake in China's development. Decades of official interaction have done little if anything to change the behavior of China's leaders.

The West must alter its approach to China. Hopes for a mature cooperative relationship have foundered on economic and security disagreements. Beijing's support for aggressive actors like North Korea and Iran, and its repression of its own people, leave no mystery about the nature of the regime.

The endgame in China may not come for years. But being on the right side of history, no matter how messy it turns out, is the wise play.

Mr. Auslin is a scholar at the American Enterprise Institute in Washington, D.C. and a columnist for WSJ.com.

This article first appeared in the Wall Street Journal.