Sun Zhengcai, the Chongqing party boss abruptly removed from office on Saturday, had been seen as a potential candidate for elevation at the autumn congress and as a possible future premier, but his star had waned since coming under criticism from the anti-corruption watchdog.

The government has yet to say what has happened to Sun.

Sources with ties to the leadership and foreign diplomats say Sun has been out of favour after the CCDI criticized Chongqing authorities in February for not doing enough to root out lingering “poisonous” influence from a disgraced predecessor, Bo Xilai.

Bo was once himself a contender for top leadership before being jailed for life in 2013 in a dramatic corruption scandal.

Xi’s crackdown on corruption has seen dozens of senior officials jailed, reaching right into the upper echelons of the party. Xi has warned, like others before him, that the problem is so serious it could affect the party’s grip on power.

Wang agreed with that assessment in his article.

“The greatest challenge to our party ruling for a long time and ruling fully is effective supervision,” he wrote.

Exposing problems shows the party’s confidence in facing them, Wang said.

“Putting out there the problems that objectively exist shows a high level of self-confidence and staunch focus, winning over the faith, trust and confidence of the people in the party’s centre,” he wrote, referring to the party’s top leadership.

The crackdown has not just been focused on issues like bribery and using public money to fund lavish lifestyles. It has also taken aim at those whose political loyalty is found lacking or who express doubt in public about party policies.

Wang said some party members practised “political nihilism”, casting aside their beliefs, while others were guilty of “phoney politics”, seeing the word of the leadership as nothing more than slogans.

The party has long said it alone can deal with corruption, dismissing any calls for an independent body separate from the party to tackle the issue.