Voting opens in Botswana for a hotly contested general election that could test the country's traditionally stable politics, as the ruling party faces its toughest challenge yet. The historic Botswana Democratic Party (BDP) -- whose rule has been unfettered since independence from Britain in 1966 -- was shaken up earlier this year after former president Ian Khama dramatically renounced his hand-picked successor Mokgweetsi Masisi.