The Democratic Republic of Congo was headed Sunday into a crucial week, with President Joseph Kabila set to declare whether he will run again in elections as one key challenger returned home and another was banned.

The DRC was thrown into a crisis nearly two years ago when Kabila refused to step down.

And it has been further roiled by the return of former vice president Jean-Pierre Bemba, 55, freshly acquitted of war-crimes convictions in The Hague, who flew back to Kinshasa for a brief visit to lodge his candidacy for the December 23 elections. He is due to head back to Europe this week.

Another key rival is Moise Katumbi, a powerful former governor of mineral-rich Katanga province — who has been living in self-imposed exile after falling out with Kabila.

But his supporters are incensed after authorities twice barred him from returning, and said he could be arrested if he sets foot in the country.

“Katumbi tried to come back, no-one can criticise him for doing what he needed to do, we are now waiting to see what happens on Wednesday,” said a diplomatic source in Kinshasa who doesn’t believe Kabila will reveal his plans by the set deadline.

“Katumbi is seen as the main challenger because he is from the east of the country, like Kabila, and can galvanise support there,” said Georges Kapiamba, human rights lawyer and president of the Congolese Association for Access to Justice.

He said the 53-year-old would likely join forces with another major political player, Felix Tshisekedi, 55 — an alliance that would pose a hefty threat to Kabila or his chosen successor.

The DRC is one of the world’s most volatile countries and worries about the elections run deep, with many observers fearing it could spiral once more into bloodshed.

The vast country has never known a peaceful transition of power since it gained independence from Belgium in 1960.

In the space of one generation, it was gripped by two wars that sucked in countries from around the region.

Many provinces are already in the grip of armed conflict and millions have had to flee their homes, many flocking to Uganda, Tanzania, Angola and Zambia.

A regional summit has been scheduled for mid-August, and the DRC elections are likely to dominate the agenda.

Last month, the UN’s High Commissioner for Human Rights, Zeid Ra’ad Al Hussein, warned of “numerous violations of human rights norms and principles” in the DRC, raising “serious doubts about the credibility of the country’s long-delayed elections”.

The level of anxiety today is “the worst in 20 years”, said the head of a political NGO who has lived in the DRC for two decades.

Kabila, who took the helm in 2001 from his assassinated father, Laurent-Desire Kabila, was meant to step down at the end of 2016 at the end of his second mandate.

But he has stayed in office, invoking a constitutional clause to stay in power until a successor is elected, and provoking protests that have been suppressed with deadly fire.

As Wednesday’s midnight deadline looms, there are growing fears Kabila, 47, could claim he has only completed one term under a revised constitution and run again.

To do so would “heighten the risk of large-scale violence and instability, with potentially devastating consequences across the region”, said Ida Sawyer, Central Africa director at Human Rights Watch.

But Congolese political analyst Jean-Claude Mputu said it was “still possible he could choose a successor. He knows his (own) candidacy would be the end of a seemingly legitimate electoral process”.

The international community, in particular the United States, has been calling on Kabila to step aside.

Kabila recently postponed a visit by UN Secretary General Antonio Guterres but this week made a visit to Angola, a country with which he is traditionally allied, to confer with President Joao Lourenco.

Whether it is Kabila or his hand-picked successor who runs, the opposition will have to unite as December approaches — a task that will require challengers to overcome policy or personal differences and rally their supporters to a compromise.

“This election will be highly competitive,” said Paul Fagan, director of the Human Rights and Democracy programs for the McCain Institute for International Leadership at Arizona State University.

“If there are several high-profile candidates like Jean-Pierre Bemba, Moise Katumbi, Felix Tshisekedi, Vital Kamerhe and Joseph Kabila, then that bodes well for Kabila or his chosen successor since it’s a winner-take-all situation.

Several opposition candidates will split the vote.”

In a recent poll conducted by CRG/BERCI, Katumbi and Tshisekedi tied at 19 percent of votes nationwide. Bemba polled at 17 percent and Kabila was at 9 percent.

Overshadowing the vote is a widespread distrust of the electoral process in a country where contested results have led to political deadlock or violence.

Nearly two-thirds of voters — 62 percent — do not trust the National Independent Electoral Commission (CENI) to conduct free and fair elections.

There are also significant logistical and security challenges with organising the elections.

But “there’s little MONUSCO can do in this situation except refuse to participate in electoral preparations,” which would be a last-ditch option, said Fagan, referring to the world’s largest UN peacekeeping operation.

Registration by August 8 is only the first step for presidential hopefuls.

CENI will then have to validate each candidate, before a definitive list is scheduled to be published on September 19.