Botswana will hold a general election on Wednesday with President Mokgweetsi Masisi competing against three challengers for a second term in the diamond-rich southern African state.

The poll could be competitive, analysts said, although a divided opposition gives the advantage to Masisi's Botswana Democratic Party (BDP), which has ruled the country of 2.3-million people since its independence from Britain in 1966.

Botswana has enjoyed stability and relative prosperity thanks to its diamond wealth and small population, which gets free healthcare and education. It is the world's top producer by value of the gem.

But a downturn in the diamond market has put a squeeze on revenues in the last few years, and the country has struggled to diversify its economy. Opponents say the BDP has been in power too long and accuse it of economic mismanagement and corruption, which it denies.

"Our diamonds have not been selling since April so yes, our revenues are down but the economic fundamentals still remain intact," said Masisi at a presidential debate last week.

"We are going to continue with the projects and policies we have come up with that are aimed at putting more money and wealth into the hands of the citizens of this country," he said.

One success of his first term was negotiating a new contract with diamond giant De Beers which will give Botswana a greater share of its rough diamonds. He also lifted a ban on elephant hunting which he says benefits rural communities, and instated an import ban on some produce items to help farmers.

His main challenger is Duma Boko of the opposition coalition Umbrella for Democratic Change (UDC).

The other candidates are Dumelang Saleshando of the Botswana Congress Party and Mephato Reatile of the Botswana Patriotic Front, backed by former President Ian Khama who quit the BDP after a feud with Masisi over scrapping the hunting ban and other issues.

Opponents have attacked Masisi's economic record, citing rising unemployment, which stands at around 28%.

"It is not acceptable that a country such as ours which is the fifth richest per capita in Africa still has so many people living in poverty," said Boko at the debate.

Botswana actually has the fourth highest gross domestic product (GDP) per capita of countries in sub-Saharan Africa, according to World Bank figures.

Boko has pledged to more than double the minimum wage and increase social grants, saying he would get the money by reducing wasteful spending.

The BDP has faced declining popularity but maintains a large majority in parliament, having won 38 of the 57 contested seats in 2019. The UDC won 15 seats. Voters in Botswana elect parliamentarians, who then elect the president.

Analysts said the opposition is crippled by a lack of funding.

"The playing field is not even," said Ringisai Chikohomero, from the South Africa-based Institute for Security Studies.

After the last election the opposition claimed fraud and challenged the results at the High Court, which dismissed the case.