There was no shortage of smiles and cheers as Felix Tshisekedi and Vital Kamerhe on Friday made their way into a room packed with cameras in Nairobi.

But as soon the two Congolese opposition stalwarts took to the microphone to announce their decision to join forces in the country’s long-delayed December 23 presidential election, the jubilation could also be felt far beyond the Kenyan capital.

The news prompted scenes of joy in Kinshasa, the capital of the Democratic Republic of Congo (DRC) thousands of kilometres away, where the politicians’ supporters took to the streets to celebrate the freshly-formed partnership.

The sight was in stark contrast with what unfolded some two weeks ago, when Tshisekedi’s supporters had again poured to the streets – this time, to denounce their leader’s decision to throw his support behind member of parliament Martin Fayulu after high-level opposition talks in Switzerland.

Barely 24 hours after those protests, both Tshisekedi and Kamerhe withdrew their signature from the agreement in Geneva, shattering a rare moment of unity for the DRC’s traditionally fractured opposition. 

Their teaming up now is expected to not only have decisive implications for the candidacy of Fayulu – who is still backed by several opposition heavyweights – but also that of Emmanuel Ramazani Shadary, the anointed successor of long-time incumbent President Joseph Kabila.

According to an opinion poll published by the US-based Congo Research Group last month, Tshisekedi is the most popular candidate by a distance (36 percent), trailed by Kamerhe in second place (17 percent). Shadary follows with 16 percent, while Fayulu is forecast to win eight percent.

As election season heats up, amid warnings over a “hostile political environment” and analysts’ reservations about the prospect of a free and fair vote, we take a look at the leading candidates in the race to succeed Kabila.

Felix Tshisekedi

Tshisekedi, the son of late veteran opposition politician Etienne Tshisekedi, has promised to restore the rule of law and fight the “gangrene” of corruption in the resource-rich DRC.

He has also pledged to end long-running conflicts in the country’s eastern North and South Kivu provinces, which – combined – border Uganda, Rwanda and Burundi, and are home to more than 100 active armed groups, according to Human Rights Watch.

If Tshisekedi tops the DRC’s first-past-the-post vote, he appears likely to take a hard line on dealing with Kabila’s divisive legacy.

Last year, he told the AFP news agency that he would set up a “truth and reconciliation commission” to call Kabila to account for his tenure, though would also allow him to remain in the country.

His opponents, however, argue he has inadequate experience having never held high office and would be ill-suited for dealing with the the country’s grinding poverty and several humanitarian crises.

For his part, campaign director Kamerhe – who is lined up to become prime minister in the case of Tshisekedi win, said on Friday’s press conference that the pair would “run Congo differently” and “break with bad governance”.

“We are not among those who say, ‘We come to power, it’s our turn to eat!” he told reporters.

Martin Fayulu

A former oil executive, Fayulu emerged as the somewhat surprise candidate of choice for the anti-Kabila front at the conclusion of the summit in Geneva on November 11.

DespiteTshisekedi and Kamerhe’s withdrawal, the remaining members of the alliance – including popular heavyweights Jean-Pierre Bemba and Moise Katumbi – have continued to back the 62-year-old’s bid for office.

They have also sought to broaden their support base by aligning with civil society groups and working with the country’s influential Catholic Church network.

Fayulu, a member of parliament with considerable grassroots support in Kinshasa, is known for his staunch opposition to the planned use of a new electronic voting system in this election, alleging it may be more vulnerable to vote-rigging than traditional pen and paper ballots.

Election officials have dismissed the criticism, saying the use of more than 100,000 South Korean-made touchscreen voting machines will cut down on election costs and the waiting period for results.

A fiery critic of Kabila, Fayulu has also routinely featured at the front of marches against the incumbent president. He has been arrested several times during opposition demonstrations in Kinshasa and elsewhere, once being struck in the head with a rubber bullet.

Kabila’s ruling coalition, however, appears unfazed by Fayulu’s challenge, with leading officials saying they are “not worried” following the announcement of his candidacy.

Emmanuel Ramazani Shadary

Shadary is a long-term Kabila ally and a central part of the ruling Common Front for Congo (FCC) coalition apparatus.

The 57-year-old has held several roles in the People’s Party for Reconstruction and Democracy (PPRD), a party he cofounded with Kabila and which heads the FCC.

As interior minister, a position he held from January 2017 until February of this year, he oversaw several violent crackdowns on anti-government protesters riled by Kabila’s refused to step down from office when his second and final constitutional term officially expired in December 2016.

The European Union sanctioned him for his role in the repression of the protests, during which security forces killed scores of anti-government demonstrators, and accused him of being involved in “planning, directing, or committing acts that constitute serious human rights violations in DRC”.

Shadary has vowed to reinforce the authority of the state and diversify the economy, as well as create much-need jobs, tackle poverty and guarantee access to public services.

He remains a largely unknown figure in the vast expanse of the DRC with meagre financial means and no substantial independent base of support.

Analysts have speculated his relative anonymity is being harnessed by Kabila, who they suggest is seeking to create a “new political class” and, crucially, one indebted to the long-term leader for his support.

Leaders from the 28 current European Union member states are set to meet on Sunday in Brussels for an emergency summit to finalise a deal on Britain’s departure from the bloc, or Brexit.

In what is seen as the latest chapter in the long-running Brexit saga, the leaders are due to vote on the draft texts agreed by both sides after months of complex and arduous negotiations.

The UK is due to leave the EU on March 29, 2019.

Here, Al Jazeera takes a look at what to expect at the key Brussels summit.

What’s on the agenda?

The deal consists of two separate documents which have been drafted and agreed by negotiators from the UK and the EU in the past two weeks.

The first one is the withdrawal agreement, also known as the “divorce” deal. This document sets out the terms of Brexit in the wake of a landmark June 2016 referendum, which saw 52 percent of voters opting to leave the club the UK had joined in 1973.

At 585 pages long, it is by far the longer of the two documents on the table on Sunday.

The legally binding text deals with a number of issues, including citizens’ rights, the so-called “divorce settlement” and a mechanism to prevent a hard border between Ireland and Northern Ireland being implemented in the future, known as the “backstop”.

It also includes details on the length of Britain’s transition period, whereby no major changes will be made to the UK-EU relationship, as the two parties work out a post-Brexit trade deal.

That period is currently set to last from March 2019 until December 2020, although the length of the transition could change at Sunday’s summit.

The second document is the political declaration, an aspirational, non-legally binding text that sets out the terms of the future relationship between the EU and the UK over 26 pages.

It deals with ambitions for a future trading relationship, as well as close ties on foreign policy, criminal justice, law enforcement, security and defence.

What will happen on Sunday?

The leaders of the EU member states are due to vote on both texts.

In the days before the summit, some states raised objections regarding the content of the withdrawal agreement, including over the issue of fishing rights in the UK’s territorial waters post-Brexit.

The Europeans want to secure the same access to fishing waters around Britain that they currently enjoy, and have tried to tie the issue to a future trade deal with it.

Meanwhile, Spain had threatened to pull out of the summit altogether until it was given assurances over Gibraltar, although the issue appeared to have been resolved on Saturday.

If they reach a deal, will Brexit be over?

Not by a long way.

The British Prime Minister Theresa May will still have to get the deal approved by the UK parliament, where she faces a formidable task to win a majority in the 650-member House of Commons.

Domestically, the prime minister’s draft deal has been attacked from all sides. Dozens of May’s 315 Conservative MPs are expected to vote against the deal, as is the opposition Labour Party.

Northern Ireland’s Democratic Unionist Party (DUP), which props up May’s coalition government with 10 MPs, has also indicated it will vote against the deal. On Saturday, the DUP urged May to “bin the backstop”.

The parliamentary vote is likely to take place in early-to-mid December.

What could happen next?

If the UK parliament approves the deal, which seems unlikely, then the British government would propose new legislation in January, which would then need to be approved by parliament before it becomes law. It would then need to be ratified by the EU before Brexit Day on March 29.

If MPs in the UK reject the deal, as seems highly likely at this stage, then a number of scenarios could play out.

Jeremy Corbyn’s Labour would likely push for a general election to be held as soon as possible.

Conservatives could look to either unseat May as leader of the party, or try and amend the Brexit deal before bringing it for a second vote in parliament. 

Meanwhile, campaigners for a second referendum on Brexit would likely also intensify their efforts to secure a new public vote, including the option for the UK to remain in the EU.

It remains to be seen whether politicians or the public have the appetite for a second referendum.

With Britain scheduled to leave the EU in March, there will not be much time for British leaders to act. If the UK reaches that date without a deal in place, then it will still leave the EU.

A so-called “no-deal Brexit” is widely predicted to prove catastrophic for the UK and is seen as an option that pretty much all sides are desperate to avoid.