Robert Mugabe, one of Africa’s longest-serving, and worst, presidents is gone after 37 years of misruling the southern African country of Zimbabwe. That is cause for rejoicing.

It was not a voluntary retirement. In late November, the Zimbabwe National Army swooped into the capital, Harare, to arrest him, his wife (and heir-apparent) Grace, and a number of politicians associated with Grace. The coup was the latest development in a yearslong battle within the ruling ZANU-PF party over who would succeed Mr. Mugabe, who is 93.

Sadly, Mr. Mugabe’s successor is unlikely to be much of an improvement. The military installed as the new leader former Vice President Emmerson Mnangagwa, one of Mr. Mugabe’s most brutal enforcers.

In the 1980s, Mr. Mnangagwa was central to the Gukurahundi massacre campaign in opposition stronghold areas of Zimbabwe. At least 20,000 people died in that campaign. Mr. Mnangagwa was also allegedly the man behind the terrible violence ZANU-PF unleashed against the opposition during a runoff election in 2008. He has been under U.S. sanctions for nearly 15 years for “undermining democratic processes or institutions.”

Institutionally, the ZANU-PF system that enthusiastically empowered Mr. Mugabe remains intact. Mr. Mnangagwa is a long-standing party pillar, and now its head, and Mugabe-era ZANU-PF officials, dominate the Cabinet he announced on Nov. 30.

The coup also appears to have only strengthened the kleptocratic and abusive Zimbabwean military. Mr. Mnangagwa rewarded his patrons by appointing two senior officers to the Cabinet: Maj. Gen. Sibusiso Moyo, who announced the coup on Zimbabwean television, and Air Marshal Perrance Shiri, who led the brigade responsible for the Gukurahundi massacre.

As bleak as the situation is, there are some opportunities for Zimbabweans who want a free and democratic country. The divisive succession struggle likely weakened ZANU-PF at least temporarily. The party’s 2015 expulsion of former presidential contender Joice Mujuru likely shrank its base with voters loyal to her. Doubtless, there are more than a few Mugabe devotees now disgruntled over the party’s treatment of their heroes.

Mr. Mnangagwa also faces a difficult task ahead. He has promised to follow through with scheduled elections next year, but he is unlikely to win them given his unpopularity with many Zimbabweans familiar with his brutality. That means he will either have to delay the contest or steal a page from the old ZANU-PF playbook.

Certainly, he will need as much ZANU-PF and military support as he can muster. That will require resuscitating the patronage networks that sustained Mr. Mugabe in power. Given the blighted state of the Zimbabwean economy, that could be difficult.

Zimbabwe also has a feisty civil society that Mr. Mugabe was unable to crush, and a number of competent and accomplished opposition figures. However, the opposition has frequently been divided; it must heal those rifts if it is to have a chance to seize the opportunity.

The difficult task before the international community is to use what little leverage it has to help pressure Mr. Mnangagwa into staging genuinely equitable elections — for the first time in nearly four decades.

Until there are signs of progress, the U.S. should not lift any of the sanctions it has on Zimbabwe’s leadership. Washington should work with its allies that have interests in Zimbabwe to bring concerted pressure on the regime. It can also offer economic and diplomatic support to kick in after a free and fair election.

Only Zimbabweans can break the ZANU-PF stranglehold on their country. Doing so will be difficult, and it will not be accomplished overnight. It will require the many Zimbabweans who resisted Mr. Mugabe’s regime to continue striving for a free Zimbabwe.

The U.S. and the rest of the international community should do what it can to support their efforts to prevent one dictator from replacing another.