It is a contest that will be familiar to many – not just in Angola but in every country across Africa where anyone remembers the cold war.

It pits the People’s Movement for the Liberation of Angola (MPLA), the political party that has ruled the southern African country for more than four decades, against the National Union for the Total Independence of Angola (Unita), which has been battling to gain control for more than 50 years.

The two are no longer warring over trenches, airstrips and dusty roads through scrubby forests, but fighting for the backing of 9 million voters as Angola goes to the polls on Wednesday to elect a new president.

Angola’s civil war lasted more than 25 years, ending in 2002, leaving the country devastated. Since then more than $100bn has been spent on reconstruction. The stakes are now not quite as high as when MPLA troops, backed by Cuba and the Soviet Union, clashed with Unita forces, supported by South Africa and the US, in the 1980s, but few doubt the importance of the poll.

“It would be extremely surprising if the MPLA loses power, but this is the first time in the past 40 years where there is uncertainty over what happens next,” said Søren Kirk Jensen, an expert on Angola at the independent policy institute Chatham House.

One major change will follow the poll. After 38 years in power, José Eduardo dos Santos is not seeking re-election. The 74-year-old has guided the MPLA from hardline Marxism to a rapacious capitalism that enemies say has been tarnished by cronyism, nepotism and corruption. Now, weakened by illness, he is stepping down.

Dos Santos was Africa’s longest-serving president after Equatorial Guinea’s Teodoro Obiang Nguema Mbasogo. Unless Unita can win the poll, dos Santos’s place will be taken by 63-year-old João Lourenço, the defence minister.

Supporters of Joao Lourenço, presidential candidate of the ruling MPLA. Photograph: Manuel de Almeida/EPA

It is Lourenço’s image that graces almost all the election posters splashed across the capital, Luanda, and other cities in Angola. Far fewer show Unita’s candidate, Isaías Samakuva, and many of these have been defaced.

Even some critics of the MPLA see Lourenço’s likely election as a turning point. “The MPLA has made so many mistakes; there is so much corruption. It will be impossible for [Lourenço] to make as many errors,” said Marcolino Moco, a former prime minister and party official who in now a fierce opponent of dos Santos.

Lourenço joined the MPLA as a teenager and fought in the independence struggle against Portugal and the civil war with Unita that followed. Along with hundreds of other cadres, he later studied in the Soviet Union before rising up the ranks in the military and the party, navigating the MPLA’s swing from leftism to market capitalism with success. He has a reputation for relative probity and is respected by the army.

Dos Santos, who remains president of the party, will retain significant powers and his family is expected to maintain its hold on a huge business empire. Dos Santos’ daughter Isabel runs the enormous state oil company and is reported to be Africa’s richest woman. “There won’t be a revolution,” Jensen said.

In a recent interview with the Washington Post, Lourenço said the MPLA was “working towards a comfortable victory” in the elections. His confidence appears justified. Unita won just 18% in the last election, in 2012, against the MPLA’s 72%.

There is widespread concern about the fairness of the electoral process. The government has deployed state resources on a huge scale and has consistently repressed critics, moving on 12 August to ban protests and demonstrations by groups not running in the polls.

In a document distributed to the media and quoted by Angola Press News Agency, the interior ministry said street protests planned by activists posed a security risk and “may clash with activities of political parties”.

A new law has given regulatory control of all media to a body controlled by the government and the ruling party. The campaign group Human Rights Watch said the election will be “marred by severe restrictions on freedom of expression and assembly, and limited access to information due to government repression and censorship”.

Unita officials say they have already complained about the inconvenient allocation of polling stations to voters, who sometimes live in different provinces, and problems registering Unita representatives to accompany the vote. The European Union has also scrapped plans to observe the elections after Luanda failed to agree to a package of conditions, including access to all parts of the country during the poll. It will send a small team of experts instead.

However, the biggest threat to the MPLA is its failure to manage Angola’s economy. The state, Africa’s second-biggest producer of crude oil, has been hit hard by the global fall in oil prices, with revenues crashing from $60bn three years ago to $27bn in 2016. After years of surging growth, Angola has slipped into recession. One recent symptom of the poverty that 15 years of inefficient and expensive investment have failed to eradicate was an outbreak of yellow fever, among the world’s worst in decades, though the disease can be prevented by a single inoculation.

Poor people, many of them still living in shanty towns visible from the glittering office blocks and luxury hotels that line Luanda’s corniche, have been hit by inflation that peaked at 42% last year, steeply increasing the cost of rent and basic foodstuffs.

The income of the new middle classes – including vast numbers of civil servants, soldiers and teachers on the state payroll – has dropped steeply in real terms as salaries have remained unchanged. The elite have suffered too. Sales of hugely expensive European-made luxury cars have plummeted, dealers in Luanda say.

In one recent poll, nearly 90% of respondents said the MPLA leadership acts in its own interest, and not in that of the state or the Angolan people.

Unita is campaigning on a broad platform for change, promising to increase spending on education and health, combat corruption and open the economy to more foreign investment. Yet it is unclear where funding for this would come from.

“We need to have an opposition that is capable of stopping certain acts which constitute abuses of power,” Samakuva, Unita’s presidential candidate, said last week, adding that he would welcome working with Angola’s second opposition party, the Broad Convergence for the Salvation of Angola – Electoral Coalition (Casa-Ce), to form a coalition government if necessary.

Casa-Ce won 6% in 2012, at its first appearance on the ballot, but the few polls available suggest it should gain ground this time, attracting younger urban voters disillusioned by the two main parties.

The economic crisis also undermines the system of political patronage that underpins MPLA rule, said Francisco Miguel Paulo, an economist at the Catholic University of Angola, because it reduces the government’s ability to invest in projects that “benefit the lives of people and bring it popularity”.

“There was a time when Angola had a lot of money and the government had the chance to make a difference. That opportunity was missed,” Paulo said.

But the crisis has also focused minds. Soren of Chatham House said the political elite has realised “the party is over”.

“Lourenço is coming with a mandate … to do things differently. It is not fair to say this is simply cosmetic,” he said.

Any change is likely to be gradual, said Moco, the former prime minister.

“It will be slow and difficult. But we have to have some hope. We have to try. We have to hope.”