Rwandan President Paul Kagame waves to supporters during a rally this month in Nyanza, Rwanda. (Jean Bizimana/Reuters)

Brian Klaas is a fellow in comparative politics at the London School of Economics and author of “The Despot’s Accomplice: How the West is Aiding and Abetting the Decline of Democracy.”

Next week, Rwandans will go to the polls in a sham election and almost certainly reelect President Paul Kagame.

Kagame has been in power since 1994, when he became vice president in the aftermath of the horrors of the Rwandan genocide. International donors love him because he has been successful at combating corruption and promoting economic growth. But he’s also guilty of serious abuses. His enemies often die mysterious deaths, sometimes with signs of torture. There is strong evidence that he has dispatched hit men to kill Rwandan dissidents in both South Africa and Britain. More recently, Kagame has changed Rwanda’s constitution, potentially allowing him to stay in power through 2034 — a grand total of 40 years.

This raises an important question: What can be done to stop African autocrats like Kagame from simply refusing to step down when they are supposed to?

In countries where democracy hasn’t yet taken root, term limits are essential. In Africa, the fight over them is intensifying. Gray-haired strongmen are crushing the democratic aspirations of their people. But term limits can give democracy a fighting chance against entrenched autocrats.

When respected, term limits work. Research on African elections by Professor Nic Cheeseman at the University of Birmingham has shown that peaceful transfers of power through the ballot box are far more likely when incumbents are not on the ballot.

Term limits are still important even when despots bend or break them. Normally, it’s daunting for citizens to remove a ruler who has been in power for decades. But term limits provide a precise pressure point: When the president tries to change the rules, people can take to the streets in opposition to something specific.

Without that leverage, many African leaders severely overstay their welcome. Just take Zimbabwean President Robert Mugabe. He has been in power (first as prime minister, then as president) since 1980 — back when Jimmy Carter was still in the White House. When pressed by a reporter on whether it might finally be time to say goodbye to the people of Zimbabwe after more than three decades in power, he reportedly replied: “Why? Where are they going?”

Eight of out 10 Zimbabweans have never lived under the rule of anyone other than Mugabe. The proportion is even higher in Angola, led by José Eduardo dos Santos since 1979. Teodoro Obiang of Equatorial Guinea took power that same year. But Paul Biya of Cameroon wins the despotic dinosaur prize, ruling Cameroon (first as prime minister, then as president) since 1975 — back when Gerald Ford was in office.

Despite African political instability, seven of the 10 longest-serving rulers in the world are African. African democracy, or the lack of it, has suffered accordingly.

Over the past several decades, Western governments have pushed for democratic reforms in Africa. In response to that pressure and calls from their own citizens, 18 African countries instituted constitutional two-term limits aimed at stopping future Mugabes from holding office as long as they want.

But in Africa, rules are far too easily bent or broken. With alarming frequency, African autocrats are trying a new playbook — simply changing term-limit rules or ignoring them to stay in power. At least 16 African heads of state have tried to remain in power by tweaking the constitution. Leaders succeeded in doing so in the Republic of the Congo, Congo, Rwanda, Burundi, Djibouti, Cameroon, Chad, Uganda, Gabon and Togo. As they do so, democracy continues to recede from the continent while economic growth and human rights suffer.

Africans are striking back. Across the continent, opinion surveys show that more than two-thirds of citizens approve of term limits for their heads of state. In both Burkina Faso and Burundi, presidents who defied term limits have triggered serious popular unrest. Since the rules are already in place, people can take to the streets when the autocrat tries to change them. That’s easier than pushing for a new rule.

Last year, Joseph Kabila, president of Congo, pledged to step down and hold elections after pressure from the Obama administration combined with widespread unrest to make his position untenable. It appeared, for a time, that the one-two punch of U.S. foreign policy and local street protests could make despots think twice about violating term limits.

That changed on Nov. 8, 2016. Pressure from Obama, the lame-duck president, became meaningless. President Trump signaled that he wouldn’t lift a finger to deal with problems outside narrowly defined interests. In his transactional view of diplomacy, term limits simply don’t rate.

This is a momentous lost opportunity. These countries aren’t like North Korea or Kazakhstan, where term limits were never realistic. Decades of foreign policy pressure in Africa have paid off. Now the time has come to push governments to obey their own rules. Trump derides career politicians and claims he wants to drain the swamp in Washington. But with virtually no effort and very little cost, Washington can do its part to help Africans get rid of their own, much more insidious career politicians. We should help Africa drain their swamps so that democracy can grow.