The BDP is one of the longest-serving ruling parties in Africa, having been in power for the last 58 years since independence from the United Kingdom in 1966.
A flagging economy and climate change are the two major challenges facing the country.
The one-day election decides who sits in parliament, and then lawmakers will later elect the president. Incumbent president Mokgweetsi Masisi, a former high school teacher and United Nations worker, is hoping for a second and final term.
Botswana has long been heralded as a success story in the region for its stable politics and economy, but a global downturn in demand for diamonds in recent years compounded with the rising cost of living, has seen unemployment skyrocket to 27%.
In response, the BDP has promised to diversify the economy that has become increasingly dependent on the diamond trade.
The landlocked country is at particular risk due to climate change, which is worsening desertification in sub-Saharan Africa.
Masisi will face three main challengers: Duma Boko of the main opposition Umbrella for Democratic Change party, Dumelang Saleshando of the Botswana Congress Party and Mephato Reatile from the Botswana Patriotic Front.
The election is expected to reignite the feud between Masisi and ex-president Ian Khama.
Khama accused Masisi of becoming increasingly authoritarian, and was later charged with illegal possession of a firearm and receiving stolen property. Khama has said the charges are politically motivated, and returned from exile in South Africa to campaign for the Botswana Patriotic front.